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This rule detects the deletion of the authorized_keys or authorized_keys2 files on Linux systems. These files are used to store public keys for SSH authentication. Unauthorized deletion of these files can be an indicator of an attacker removing access to the system, and may be a precursor to further malicious activity.
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This rule detects the use of system search utilities like grep and find to search for AWS credentials inside a container. Unauthorized access to these sensitive files could lead to further compromise of the container environment or facilitate a container breakout to the underlying cloud environment.
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Container Management Utility Run Inside A Container
This rule detects when a container management binary is run from inside a container. These binaries are critical components of many containerized environments, and their presence and execution in unauthorized containers could indicate compromise or a misconfiguration.
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This rule detects when chmod or chown are used to add the execute permission to a file inside a container. Modifying file permissions to make a file executable could indicate malicious activity, as an attacker may attempt to run unauthorized or malicious code inside the container.
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This rule detects the use of the built-in Linux DebugFS utility from inside a container. DebugFS is a special file system debugging utility which supports reading and writing directly from a hard drive device. When launched inside a privileged container, a container deployed with all the capabilities of the host machine, an attacker can access sensitive host level files which could be used for further privilege escalation and container escapes to the host machine.
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This rule detects the use of the mount utility from inside a container. The mount command is used to make a device or file system accessible to the system, and then to connect its root directory to a specified mount point on the local file system. When launched inside a privileged container--a container deployed with all the capabilities of the host machine-- an attacker can access sensitive host level files which could be used for further privilege escalation and container escapes to the host machine. Any usage of mount inside a running privileged container should be further investigated.
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Identifies the use of a compression utility to collect known files containing sensitive information, such as credentials and system configurations inside a container.
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This rule detects the use of system search utilities like grep and find to search for private SSH keys or passwords inside a container. Unauthorized access to these sensitive files could lead to further compromise of the container environment or facilitate a container breakout to the underlying host machine.
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This rule detects an SSH or SSHD process executed from inside a container. This includes both the client ssh binary and server ssh daemon process. SSH usage inside a container should be avoided and monitored closely when necessary. With valid credentials an attacker may move laterally to other containers or to the underlying host through container breakout. They may also use valid SSH credentials as a persistence mechanism.
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This rule detects commonly abused network utilities running inside a container. Network utilities like nc, nmap, dig, tcpdump, ngrep, telnet, mitmproxy, zmap can be used for malicious purposes such as network reconnaissance, monitoring, or exploitation, and should be monitored closely within a container.
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Unusual Interactive Process Launched in a Container
This rule detects when an unusual interactive process is launched inside a container. Interactive processes are typically run in the foreground and require user input, which is unusual behavior for a containerized environment. This activity could indicate an attacker attempting to gain access to the container environment or perform malicious actions.
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This rule monitors the creation of shared object files by previously unknown processes. The creation of a shared object file involves compiling code into a dynamically linked library that can be loaded by other programs at runtime. While this process is typically used for legitimate purposes, malicious actors can leverage shared object files to execute unauthorized code, inject malicious functionality into legitimate processes, or bypass security controls. This allows malware to persist on the system, evade detection, and potentially compromise the integrity and confidentiality of the affected system and its data.
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This rule detects when a base64 decoded payload is piped to an interpreter on Linux systems. Adversaries may use base64 encoding to obfuscate data and pipe it to an interpreter to execute malicious code. This technique may be used to evade detection by host- or network-based security controls.
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This rule detects potential Docker socket enumeration activity by monitoring processes that attempt to interact with the Docker socket file (/var/run/docker.sock). Docker socket enumeration is a common technique used by attackers to interact with the Docker daemon and perform various operations, such as creating, starting, stopping, and removing containers. Attackers may abuse Docker socket enumeration to gain unauthorized access to the host system, escalate privileges, or move laterally within the environment.
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This rule detects the creation of files in the /var/log/ directory via process executables located in world-writeable locations or via hidden processes. Attackers may attempt to hide their activities by creating files in the /var/log/ directory, which is commonly used for logging system events.
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This rule detects a high number of egress network connections from an unusual executable on a Linux system. This could indicate a command and control (C2) communication attempt, a brute force attack via a malware infection, or other malicious activity. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects the execution of kill, pkill, and killall commands on Linux systems. These commands are used to terminate processes on a system. Attackers may use these commands to kill security tools or other processes to evade detection or disrupt system operations.
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This rule detects Linux user account credential modification events where the echo command is used to directly echo a password into the passwd utility. This technique is used by malware to automate the process of user account credential modification on Linux systems post-infection.
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This detection identifies a Linux host that has potentially been infected with malware and is being used to conduct brute-force attacks against external systems over SSH (port 22 and common alternative SSH ports). The detection looks for a high volume of outbound connection attempts to non-private IP addresses from a single process. A compromised host may be part of a botnet or controlled by an attacker, attempting to gain unauthorized access to remote systems. This behavior is commonly observed in SSH brute-force campaigns where malware hijacks vulnerable machines to expand its attack surface. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects potential port scanning activity from a compromised host. Port scanning is a common reconnaissance technique used by attackers to identify open ports and services on a target system. A compromised host may exhibit port scanning behavior when an attacker is attempting to map out the network topology, identify vulnerable services, or prepare for further exploitation. This rule identifies potential port scanning activity by monitoring network connection attempts from a single host to a large number of ports within a short time frame. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects potential subnet scanning activity from a compromised host. Subnet scanning is a common reconnaissance technique used by attackers to identify live hosts within a network range. A compromised host may exhibit subnet scanning behavior when an attacker is attempting to map out the network topology, identify vulnerable hosts, or prepare for further exploitation. This rule identifies potential subnet scanning activity by monitoring network connection attempts from a single host to a large number of hosts within a short time frame. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects the creation of .pth files in system-wide and user-specific Python package directories, which can be abused for persistent code execution. .pth files automatically execute Python code when the interpreter starts, making them a stealthy persistence mechanism. Monitoring these paths helps identify unauthorized modifications that could indicate persistence by an attacker or malicious package injection.
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This rule detects the creation and modification of sitecustomize.py and usercustomize.py, which Python automatically executes on startup. Attackers can exploit these files for persistence by injecting malicious code. The rule monitors system-wide, user-specific, and virtual environment locations to catch unauthorized changes that could indicate persistence or backdooring attempts.
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This rule detects the creation of a file in a world-writeable directory through a service that is commonly used for file transfer. This behavior is often associated with lateral movement and can be an indicator of an attacker attempting to move laterally within a network.
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This rule leverages the new_terms rule type to detect successful SSH authentications by an IP- address that has not been authenticated in the last 10 days. This behavior may indicate an attacker attempting to gain access to the system using a valid account.
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This rule leverages the new_terms rule type to detect successful SSH authentications via a public key that has not been seen in the last 10 days. Public key authentication is a secure method for authenticating users to a server. Monitoring unusual public key authentication events can help detect unauthorized access attempts or suspicious activity on the system.
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This rule leverages the new_terms rule type to detect successful SSH authentications by a user who has not been authenticated in the last 10 days. This behavior may indicate an attacker attempting to gain access to the system using a valid account.
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This rule identifies unusual destination port network activity originating from a web server process. The rule is designed to detect potential web shell activity or unauthorized communication from a web server process to external systems.
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This rule leverages ES|QL to detect unusual base64 encoding/decoding activity on Linux systems. Attackers may use base64 encoding/decoding to obfuscate data, such as command and control traffic or payloads, to evade detection by host- or network-based security controls. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects potential command execution from a web server parent process on a Linux host. Adversaries may attempt to execute commands from a web server parent process to blend in with normal web server activity and evade detection. This behavior is commonly observed in web shell attacks where adversaries exploit web server vulnerabilities to execute arbitrary commands on the host. The detection rule identifies unusual command execution from web server parent processes, which may indicate a compromised host or an ongoing attack. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule leverages ES|QL to detect the execution of unusual file transfer utilities on Linux systems. Attackers may use these utilities to exfiltrate data from a compromised system. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule detects unusual processes spawned from a web server parent process by identifying low frequency counts of process spawning activity. Unusual process spawning activity may indicate an attacker attempting to establish persistence, execute malicious commands, or establish command and control channels on the host system. ES|QL rules have limited fields available in its alert documents. Make sure to review the original documents to aid in the investigation of this alert.
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This rule leverages the new_terms rule type to detect file creation via a commonly used file transfer service while excluding typical remote file creation activity. This behavior is often linked to lateral movement, potentially indicating an attacker attempting to move within a network.
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External Alerts
Generates a detection alert for each external alert written to the configured indices. Enabling this rule allows you to immediately begin investigating external alerts in the app.
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The hosts file on endpoints is used to control manual IP address to hostname resolutions. The hosts file is the first point of lookup for DNS hostname resolution so if adversaries can modify the endpoint hosts file, they can route traffic to malicious infrastructure. This rule detects modifications to the hosts file on Microsoft Windows, Linux (Ubuntu or RHEL) and macOS systems.
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Identifies the execution of a Chromium based browser with the debugging process argument, which may indicate an attempt to steal authentication cookies. An adversary may steal web application or service session cookies and use them to gain access web applications or Internet services as an authenticated user without needing credentials.
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Identifies the deletion of WebServer access logs. This may indicate an attempt to evade detection or destroy forensic evidence on a system.
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Monitors for the deletion of the kernel ring buffer events through dmesg. Attackers may clear kernel ring buffer events to evade detection after installing a Linux kernel module (LKM).
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Adversaries may attempt to disable the Auditd service to evade detection. Auditd is a Linux service that provides system auditing and logging. Disabling the Auditd service can prevent the system from logging important security events, which can be used to detect malicious activity.
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Adversaries may attempt to disable the iptables or firewall service in an attempt to affect how a host is allowed to receive or send network traffic.
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Adversaries may attempt to disable the syslog service in an attempt to an attempt to disrupt event logging and evade detection by security controls.
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Adversaries may encode/decode data in an attempt to evade detection by host- or network-based security controls.
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This rule detects the process of copying or moving files from or to the
/bootdirectory on Linux systems. The/bootdirectory contains files that are essential for the system to boot, such as the kernel and initramfs images. Attackers may copy or move files to the/bootdirectory to modify the boot process, which can be leveraged to maintain access to the system.
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Detects when the tc (transmission control) binary is utilized to set a BPF (Berkeley Packet Filter) on a network interface. Tc is used to configure Traffic Control in the Linux kernel. It can shape, schedule, police and drop traffic. A threat actor can utilize tc to set a bpf filter on an interface for the purpose of manipulating the incoming traffic. This technique is not at all common and should indicate abnormal, suspicious or malicious activity.
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Detects the use of the chkconfig binary to manually add a service for management by chkconfig. Threat actors may utilize this technique to maintain persistence on a system. When a new service is added, chkconfig ensures that the service has either a start or a kill entry in every runlevel and when the system is rebooted the service file added will run providing long-term persistence.
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Telnet provides a command line interface for communication with a remote device or server. This rule identifies Telnet network connections to publicly routable IP addresses.
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Telnet provides a command line interface for communication with a remote device or server. This rule identifies Telnet network connections to non-publicly routable IP addresses.
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Identifies the creation of a hidden shared object (.so) file. Users can mark specific files as hidden simply by putting a "." as the first character in the file or folder name. Adversaries can use this to their advantage to hide files and folders on the system for persistence and defense evasion.
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This detection rule addresses multiple vulnerabilities in the CUPS printing system, including CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177. Specifically, this rule detects shell executions from the foomatic-rip parent process. These flaws impact components like cups-browsed, libcupsfilters, libppd, and foomatic-rip, allowing remote unauthenticated attackers to manipulate IPP URLs or inject malicious data through crafted UDP packets or network spoofing. This can result in arbitrary command execution when a print job is initiated.
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This rule detects the creation of D-Bus service files on Linux systems. D-Bus is a message bus system that provides a way for applications to talk to one another. D-Bus services are defined in service files that are typically located in default directories. The rule looks for the creation of service files that are not associated with known package managers or system services. Attackers may create malicious D-Bus services to establish persistence or escalate privileges on a system.
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This rule identifies the creation of directories in the /bin directory. The /bin directory contains essential binary files that are required for the system to function properly. The creation of directories in this location could be an attempt to hide malicious files or executables, as these /bin directories usually just contain binaries.
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Detects file creation events in the plugin directories for the Yum package manager. In Linux, DNF (Dandified YUM) is a command-line utility used for handling packages on Fedora-based systems, providing functions for installing, updating, upgrading, and removing software along with managing package repositories. Attackers can backdoor DNF to gain persistence by injecting malicious code into plugins that DNF runs, thereby ensuring continued unauthorized access or control each time DNF is used for package management.
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This rule detects the creation of Dracut module files on Linux systems. Dracut is a tool used to generate an initramfs image that is used to boot the system. Dracut modules are scripts that are executed during the initramfs image generation process. Attackers may create malicious Dracut modules to execute arbitrary code at boot time, which can be leveraged to maintain persistence on a Linux system.
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This rule detects the creation of the dynamic linker (ld.so) file. The dynamic linker is used to load shared libraries needed by an executable. Attackers may attempt to replace the dynamic linker with a malicious version to execute arbitrary code.
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Detects the copying of the Linux dynamic loader binary and subsequent file creation for the purpose of creating a backup copy. This technique was seen recently being utilized by Linux malware prior to patching the dynamic loader in order to inject and preload a malicious shared object file. This activity should never occur and if it does then it should be considered highly suspicious or malicious.
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Identifies instances where the 'find' command is started on a Linux system with arguments targeting specific VM-related paths, such as "/etc/vmware/", "/usr/lib/vmware/", or "/vmfs/*". These paths are associated with VMware virtualization software, and their presence in the find command arguments may indicate that a threat actor is attempting to search for, analyze, or manipulate VM-related files and configurations on the system.
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Identifies instances where a process named 'grep', 'egrep', or 'pgrep' is started on a Linux system with arguments related to virtual machine (VM) files, such as "vmdk", "vmx", "vmxf", "vmsd", "vmsn", "vswp", "vmss", "nvram", or "vmem". These file extensions are associated with VM-related file formats, and their presence in grep command arguments may indicate that a threat actor is attempting to search for, analyze, or manipulate VM files on the system.
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Identifies instances where the 'touch' command is executed on a Linux system with the "-r" flag, which is used to modify the timestamp of a file based on another file's timestamp. The rule targets specific VM-related paths, such as "/etc/vmware/", "/usr/lib/vmware/", or "/vmfs/*". These paths are associated with VMware virtualization software, and their presence in the touch command arguments may indicate that a threat actor is attempting to tamper with timestamps of VM-related files and configurations on the system.
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This rule monitors for the addition of an executable bit for scripts that are located in directories which are commonly abused for persistence. An alert of this rule is an indicator that a persistence mechanism is being set up within your environment. Adversaries may create these scripts to execute malicious code at start-up, or at a set interval to gain persistence onto the system.
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Monitors for kernel processes with associated process executable fields that are not empty. Unix kernel processes such as kthreadd and kworker typically do not have process.executable fields associated to them. Attackers may attempt to hide their malicious programs by masquerading as legitimate kernel processes.
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This detection rule addresses multiple vulnerabilities in the CUPS printing system, including CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177. Specifically, this rule detects suspicious file creation events executed by child processes of foomatic-rip. These flaws impact components like cups-browsed, libcupsfilters, libppd, and foomatic-rip, allowing remote unauthenticated attackers to manipulate IPP URLs or inject malicious data through crafted UDP packets or network spoofing. This can result in arbitrary command execution when a print job is initiated.
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Malware or other files dropped or created on a system by an adversary may leave traces behind as to what was done within a network and how. Adversaries may remove these files over the course of an intrusion to keep their footprint low or remove them at the end as part of the post-intrusion cleanup process.
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Detects a file being made immutable using the chattr binary. Making a file immutable means it cannot be deleted or renamed, no link can be created to this file, most of the file's metadata can not be modified, and the file can not be opened in write mode. Threat actors will commonly utilize this to prevent tampering or modification of their malicious files or any system files they have modified for purposes of persistence (e.g .ssh, /etc/passwd, etc.).
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A netcat process is engaging in network activity on a Linux host. Netcat is often used as a persistence mechanism by exporting a reverse shell or by serving a shell on a listening port. Netcat is also sometimes used for data exfiltration.
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This rule detects child processes spawned by Git hooks. Git hooks are scripts that Git executes before or after events such as commit, push, and receive. The rule identifies child processes spawned by Git hooks that are not typically spawned by the Git process itself. This behavior may indicate an attacker attempting to hide malicious activity by leveraging the legitimate Git process to execute unauthorized commands.
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This rule detects the execution of a potentially malicious process from a Git hook. Git hooks are scripts that Git executes before or after events such as: commit, push, and receive. An attacker can abuse Git hooks to execute arbitrary commands on the system and establish persistence.
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This rule detects the creation or modification of a Git hook file on a Linux system. Git hooks are scripts that Git executes before or after events such as commit, push, and receive. They are used to automate tasks, enforce policies, and customize Git's behavior. Attackers can abuse Git hooks to maintain persistence on a system by executing malicious code whenever a specific Git event occurs.
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This rule detects the creation of GRUB configuration files on Linux systems. The GRUB configuration file is used to configure the boot loader, which is responsible for loading the operating system. Attackers may create malicious GRUB configuration files to execute arbitrary code or escalate privileges during the boot process, which can be leveraged to maintain persistence on the system.
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This rule detects the generation of a new GRUB configuration file using built-in Linux commands. The GRUB configuration file is used to configure the GRUB bootloader, which is responsible for loading the Linux kernel and initramfs image during the boot process. Attackers may use these built-in utilities to generate a new GRUB configuration file that includes malicious kernel parameters or boot options, which can be leveraged to maintain persistence on the system.
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This rule detects the creation of a hidden directory via an unusual parent executable. Hidden directories are directories that are not visible to the user by default. They are often used by attackers to hide malicious files or tools.
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Identify activity related where adversaries can add the 'hidden' flag to files to hide them from the user in an attempt to evade detection.
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Hping ran on a Linux host. Hping is a FOSS command-line packet analyzer and has the ability to construct network packets for a wide variety of network security testing applications, including scanning and firewall auditing.
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This rule detects the extraction of an initramfs image using the
cpiocommand on Linux systems. Thecpiocommand is used to create or extract cpio archives. Attackers may extract the initramfs image to modify the contents or add malicious files, which can be leveraged to maintain persistence on the system.
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This rule detects the unpacking of an initramfs image using the
unmkinitramfscommand on Linux systems. Theunmkinitramfscommand is used to extract the contents of an initramfs image, which is used to boot the system. Attackers may useunmkinitramfsto unpack an initramfs image and modify its contents to include malicious code or backdoors, allowing them to maintain persistence on the system.
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Identifies when a terminal (tty) is spawned via Python. Attackers may upgrade a simple reverse shell to a fully interactive tty after obtaining initial access to a host.
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This rule monitors for the execution of commands that enable IPv4 and IPv6 forwarding on Linux systems. Enabling IP forwarding can be used to route network traffic between different network interfaces, potentially allowing attackers to pivot between networks, exfiltrate data, or establish command and control channels.
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Kernel Load or Unload via Kexec Detected
Mar 20, 2025 · Domain: Endpoint OS: Linux Use Case: Threat Detection Tactic: Persistence Tactic: Privilege Escalation Tactic: Defense Evasion Data Source: Elastic Defend Data Source: Elastic Endgame Data Source: Auditd Manager Data Source: Crowdstrike Data Source: SentinelOne Resources: Investigation Guide ·This detection rule identifies the usage of kexec, helping to uncover unauthorized kernel replacements and potential compromise of the system's integrity. Kexec is a Linux feature that enables the loading and execution of a different kernel without going through the typical boot process. Malicious actors can abuse kexec to bypass security measures, escalate privileges, establish persistence or hide their activities by loading a malicious kernel, enabling them to tamper with the system's trusted state, allowing e.g. a VM Escape.
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Detects the use of the insmod binary to load a Linux kernel object file. Threat actors can use this binary, given they have root privileges, to load a rootkit on a system providing them with complete control and the ability to hide from security products. Manually loading a kernel module in this manner should not be at all common and can indicate suspcious or malicious behavior.
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Kernel modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. This rule identifies attempts to remove a kernel module.
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This rule monitors for the potential memory dump of the init process (PID 1) through gdb. Attackers may leverage memory dumping techniques to attempt secret extraction from privileged processes. Tools that display this behavior include "truffleproc" and "bash-memory-dump". This behavior should not happen by default, and should be investigated thoroughly.
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This rule monitors for potential memory dumping through gdb. Attackers may leverage memory dumping techniques to attempt secret extraction from privileged processes. Tools that display this behavior include "truffleproc" and "bash-memory-dump". This behavior should not happen by default, and should be investigated thoroughly.
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This rule monitors for X11 forwarding via SSH. X11 forwarding is a feature that allows users to run graphical applications on a remote server and display the application's graphical user interface on their local machine. Attackers can abuse X11 forwarding for tunneling their GUI-based tools, pivot through compromised systems, and create covert communication channels, enabling lateral movement and facilitating remote control of systems within a network.
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Identifies attempts to add a user to a privileged group. Attackers may add users to a privileged group in order to establish persistence on a system.
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This rule detects manual execution of the
dracutcommand on Linux systems. Dracut is a tool used to generate an initramfs image that is used to boot the system. Attackers may usedracutto create a custom initramfs image that includes malicious code or backdoors, allowing them to maintain persistence on the system.
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This rule detects memory swap modification events on Linux systems. Memory swap modification can be used to manipulate the system's memory and potentially impact the system's performance. This behavior is commonly observed in malware that deploys miner software such as XMRig.
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Identifies suspicious usage of unshare to manipulate system namespaces. Unshare can be utilized to escalate privileges or escape container security boundaries. Threat actors have utilized this binary to allow themselves to escape to the host and access other resources or escalate privileges.
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Monitors for the execution of a netcat listener via rlwrap. rlwrap is a 'readline wrapper', a small utility that uses the GNU Readline library to allow the editing of keyboard input for any command. This utility can be used in conjunction with netcat to gain a more stable reverse shell.
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This rule detects the creation of a NetworkManager dispatcher script on a Linux system. NetworkManager dispatcher scripts are shell scripts that NetworkManager executes when network interfaces change state. Attackers can abuse NetworkManager dispatcher scripts to maintain persistence on a system by executing malicious code whenever a network event occurs.
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Nping ran on a Linux host. Nping is part of the Nmap tool suite and has the ability to construct raw packets for a wide variety of security testing applications, including denial of service testing.
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This rule identifies when the openssl client or server is used to establish a connection. Attackers may use openssl to establish a secure connection to a remote server or to create a secure server to receive connections. This activity may be used to exfiltrate data or establish a command and control channel.
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This rule detects the usage of the
opensslbinary to generate password hashes on Linux systems. Theopensslcommand is a cryptographic utility that can be used to generate password hashes. Attackers may useopensslto generate password hashes for new user accounts or to change the password of existing accounts, which can be leveraged to maintain persistence on a Linux system.
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Identifies the creation or modification of a K Desktop Environment (KDE) AutoStart script or desktop file that will execute upon each user logon. Adversaries may abuse this method for persistence.
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This rule detects the creation of Pluggable Authentication Module (PAM) shared object files in unusual directories. Attackers may compile PAM shared object files in temporary directories, to move them to system directories later, potentially allowing them to maintain persistence on a compromised system, or harvest account credentials.
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This rule detects PAM version discovery activity on Linux systems. PAM version discovery can be an indication of an attacker attempting to backdoor the authentication process through malicious PAM modules.
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This rule monitors for the creation of Polkit policy files on Linux systems. Polkit policy files are used to define the permissions for system-wide services and applications. The creation of new Polkit policy files may indicate an attempt to modify the authentication process, which could be used for persistence by an adversary.
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This rule detects Polkit version discovery activity on Linux systems. Polkit version discovery can be an indication of an attacker attempting to exploit misconfigurations or vulnerabilities in the Polkit service.
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Monitors for the execution of a file system mount followed by a chroot execution. Given enough permissions, a user within a container is capable of mounting the root file system of the host, and leveraging chroot to escape its containarized environment. This behavior pattern is very uncommon and should be investigated.
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This rule looks for the usage of common data splitting utilities with specific arguments that indicate data splitting for exfiltration on Linux systems. Data splitting is a technique used by adversaries to split data into smaller parts to avoid detection and exfiltrate data.
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This rule detects the creation or rename of the Doas configuration file on a Linux system. Adversaries may create or modify the Doas configuration file to elevate privileges and execute commands as other users while attempting to evade detection.
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Identifies the execution of the PRoot utility, an open-source tool for user-space implementation of chroot, mount --bind, and binfmt_misc. Adversaries can leverage an open-source tool PRoot to expand the scope of their operations to multiple Linux distributions and simplify their necessary efforts. In a normal threat scenario, the scope of an attack is limited by the varying configurations of each Linux distribution. With PRoot, it provides an attacker with a consistent operational environment across different Linux distributions, such as Ubuntu, Fedora, and Alpine. PRoot also provides emulation capabilities that allow for malware built on other architectures, such as ARM, to be run.The post-exploitation technique called bring your own filesystem (BYOF), can be used by the threat actors to execute malicious payload or elevate privileges or perform network scans or orchestrate another attack on the environment. Although PRoot was originally not developed with malicious intent it can be easily tuned to work for one.
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This rule monitors for potential attempts to disable AppArmor. AppArmor is a Linux security module that enforces fine-grained access control policies to restrict the actions and resources that specific applications and processes can access. Adversaries may disable security tools to avoid possible detection of their tools and activities.
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Identifies potential attempts to disable Security-Enhanced Linux (SELinux), which is a Linux kernel security feature to support access control policies. Adversaries may disable security tools to avoid possible detection of their tools and activities.
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This rule detects potential hex payload execution on Linux systems. Adversaries may use hex encoding to obfuscate payloads and evade detection mechanisms.
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Identifies the execution of mount process with hidepid parameter, which can make processes invisible to other users from the system. Adversaries using Linux kernel version 3.2+ (or RHEL/CentOS v6.5+ above) can hide the process from other users. When hidepid=2 option is executed to mount the /proc filesystem, only the root user can see all processes and the logged-in user can only see their own process. This provides a defense evasion mechanism for the adversaries to hide their process executions from all other commands such as ps, top, pgrep and more. With the Linux kernel hardening hidepid option all the user has to do is remount the /proc filesystem with the option, which can now be monitored and detected.
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Identifies the attempt to create a new backdoor user by setting the user's UID to 0. Attackers may alter a user's UID to 0 to establish persistence on a system.
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Identifies the execution of the mimipenguin exploit script which is linux adaptation of Windows tool mimikatz. Mimipenguin exploit script is used to dump clear text passwords from a currently logged-in user. The tool exploits a known vulnerability CVE-2018-20781. Malicious actors can exploit the cleartext credentials in memory by dumping the process and extracting lines that have a high probability of containing cleartext passwords.
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Identifies the execution of the unshadow utility which is part of John the Ripper, a password-cracking tool on the host machine. Malicious actors can use the utility to retrieve the combined contents of the '/etc/shadow' and '/etc/password' files. Using the combined file generated from the utility, the malicious threat actors can use them as input for password-cracking utilities or prepare themselves for future operations by gathering credential information of the victim.
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Monitors for the execution of different processes that might be used by attackers for malicious intent. An alert from this rule should be investigated further, as hack tools are commonly used by blue teamers and system administrators as well.
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This rule monitors for a set of Linux utilities that can be used for tunneling and port forwarding. Attackers can leverage tunneling and port forwarding techniques to bypass network defenses, establish hidden communication channels, and gain unauthorized access to internal resources, facilitating data exfiltration, lateral movement, and remote control.
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Identifies a Secure Shell (SSH) client or server process creating or writing to a known SSH backdoor log file. Adversaries may modify SSH related binaries for persistence or credential access via patching sensitive functions to enable unauthorized access or to log SSH credentials for exfiltration.
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Identifies an attempt to exploit a local privilege escalation in polkit pkexec (CVE-2021-4034) via unsecure environment variable injection. Successful exploitation allows an unprivileged user to escalate to the root user.
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Identifies the execution of the EarthWorm tunneler. Adversaries may tunnel network communications to and from a victim system within a separate protocol to avoid detection and network filtering, or to enable access to otherwise unreachable systems.
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Identifies suspicious commands executed via a web server, which may suggest a vulnerability and remote shell access. Attackers may exploit a vulnerability in a web application to execute commands via a web server, or place a backdoor file that can be abused to gain code execution as a mechanism for persistence.
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Monitors for the execution of background processes with process arguments capable of opening a socket in the /dev/tcp channel. This may indicate the creation of a backdoor reverse connection, and should be investigated further.
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This rule monitors for the execution of a set of linux binaries, that are potentially vulnerable to wildcard injection, with suspicious command line flags followed by a shell spawn event. Linux wildcard injection is a type of security vulnerability where attackers manipulate commands or input containing wildcards (e.g., *, ?, []) to execute unintended operations or access sensitive data by tricking the system into interpreting the wildcard characters in unexpected ways.
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Identifies processes that are capable of downloading files with command line arguments containing URLs to SSH-IT's autonomous SSH worm. This worm intercepts outgoing SSH connections every time a user uses ssh.
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This rule monitors for the execution of a suspicious sudo command that is leveraged in CVE-2019-14287 to escalate privileges to root. Sudo does not verify the presence of the designated user ID and proceeds to execute using a user ID that can be chosen arbitrarily. By using the sudo privileges, the command "sudo -u#-1" translates to an ID of 0, representing the root user. This exploit may work for sudo versions prior to v1.28.
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This rule monitors for the potential edit of a suspicious file. In Linux, when editing a file through an editor, a temporary .swp file is created. By monitoring for the creation of this .swp file, we can detect potential file edits of suspicious files. The execution of this rule is not a clear sign of the file being edited, as just opening the file through an editor will trigger this event. Attackers may alter any of the files added in this rule to establish persistence, escalate privileges or perform reconnaisance on the system.
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Potential Unauthorized Access via Wildcard Injection Detected
This rule monitors for the execution of the "chown" and "chmod" commands with command line flags that could indicate a wildcard injection attack. Linux wildcard injection is a type of security vulnerability where attackers manipulate commands or input containing wildcards (e.g., *, ?, []) to execute unintended operations or access sensitive data by tricking the system into interpreting the wildcard characters in unexpected ways.
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Identifies when a non-interactive terminal (tty) is being upgraded to a fully interactive shell. Attackers may upgrade a simple reverse shell to a fully interactive tty after obtaining initial access to a host, in order to obtain a more stable connection.
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This rule monitors for the execution of suspicious commands via screen and tmux. When launching a command and detaching directly, the commands will be executed in the background via its parent process. Attackers may leverage screen or tmux to execute commands while attempting to evade detection.
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This rule detects private key searching activity on Linux systems. Searching for private keys can be an indication of an attacker attempting to escalate privileges or exfiltrate sensitive information.
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This rule identifies processes that are backgrounded by an unusual parent process. This behavior may indicate a process attempting to evade detection by hiding its parent process.
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This rule detects the use of the setcap utility to set capabilities on a process. The setcap utility is used to set the capabilities of a binary to allow it to perform privileged operations without needing to run as root. This can be used by attackers to establish persistence by creating a backdoor, or escalate privileges by abusing a misconfiguration on a system.
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Message of the day (MOTD) is the message that is presented to the user when a user connects to a Linux server via SSH or a serial connection. Linux systems contain several default MOTD files located in the "/etc/update-motd.d/" directory. These scripts run as the root user every time a user connects over SSH or a serial connection. Adversaries may create malicious MOTD files that grant them persistence onto the target every time a user connects to the system by executing a backdoor script or command. This rule detects the execution of potentially malicious processes through the MOTD utility.
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This rule monitors for the execution of the ProxyChains utility. ProxyChains is a command-line tool that enables the routing of network connections through intermediary proxies, enhancing anonymity and enabling access to restricted resources. Attackers can exploit the ProxyChains utility to hide their true source IP address, evade detection, and perform malicious activities through a chain of proxy servers, potentially masking their identity and intentions.
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This rule detects the installation of root certificates on a Linux system. Adversaries may install a root certificate on a compromised system to avoid warnings when connecting to their command and control servers. Root certificates are used in public key cryptography to identify a root certificate authority (CA). When a root certificate is installed, the system or application will trust certificates in the root's chain of trust that have been signed by the root certificate.
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This rule detects sensitive security file access via common utilities on Linux systems. Adversaries may attempt to read from sensitive files using common utilities to gather information about the system and its security configuration.
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This rule monitors for the addition of the cap_setuid+ep or cap_setgid+ep capabilities via setcap. Setuid (Set User ID) and setgid (Set Group ID) are Unix-like OS features that enable processes to run with elevated privileges, based on the file owner or group. Threat actors can exploit these attributes to achieve persistence by creating malicious binaries, allowing them to maintain control over a compromised system with elevated permissions.
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This rule detects the creation of a simple HTTP web server using PHP or Python built-in modules. Adversaries may create simple HTTP web servers to establish persistence on a compromised system by uploading a reverse or command shell payload to the server web root, allowing them to regain remote access to the system if lost.
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This rule identifies the creation of SSH keys using the ssh-keygen tool, which is the standard utility for generating SSH keys. Users often create SSH keys for authentication with remote services. However, threat actors can exploit this tool to move laterally across a network or maintain persistence by generating unauthorized SSH keys, granting them SSH access to systems.
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This rule detects the deletion of SSL certificates on a Linux system. Adversaries may delete SSL certificates to subvert trust controls and negatively impact the system.
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This rule monitors for the usage of the sudo -l command, which is used to list the allowed and forbidden commands for the invoking user. Attackers may execute this command to enumerate commands allowed to be executed with sudo permissions, potentially allowing to escalate privileges to root.
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Detects suspicious process events executed by the APT package manager, potentially indicating persistence through an APT backdoor. In Linux, APT (Advanced Package Tool) is a command-line utility used for handling packages on Debian-based systems, providing functions for installing, updating, upgrading, and removing software along with managing package repositories. Attackers can backdoor APT to gain persistence by injecting malicious code into scripts that APT runs, thereby ensuring continued unauthorized access or control each time APT is used for package management.
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Identifies when suspicious content is extracted from a file and subsequently decompressed using the funzip utility. Malware may execute the tail utility using the "-c" option to read a sequence of bytes from the end of a file. The output from tail can be piped to funzip in order to decompress malicious code before it is executed. This behavior is consistent with malware families such as Bundlore.
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Monitors for dynamic linker discovery via the od utility. od (octal dump) is a command-line utility in Unix operating systems used for displaying data in various formats, including octal, hexadecimal, decimal, and ASCII, primarily used for examining and debugging binary files or data streams. Attackers can leverage od to analyze the dynamic linker by identifying injection points and craft exploits based on the observed behaviors and structures within these files.
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This detection rule addresses multiple vulnerabilities in the CUPS printing system, including CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177. Specifically, this rule detects suspicious process command lines executed by child processes of foomatic-rip and cupsd. These flaws impact components like cups-browsed, libcupsfilters, libppd, and foomatic-rip, allowing remote unauthenticated attackers to manipulate IPP URLs or inject malicious data through crafted UDP packets or network spoofing. This can result in arbitrary command execution when a print job is initiated.
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This rule monitors for a file creation event originating from a kworker parent process. kworker, or kernel worker, processes are part of the kernel's workqueue mechanism. They are responsible for executing work that has been scheduled to be done in kernel space, which might include tasks like handling interrupts, background activities, and other kernel-related tasks. Attackers may attempt to evade detection by masquerading as a kernel worker process.
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Monitors for grep activity related to memory mapping. The /proc/*/maps file in Linux provides a memory map for a specific process, detailing the memory segments, permissions, and what files are mapped to these segments. Attackers may read a process's memory map to identify memory addresses for code injection or process hijacking.
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Identifies service creation events of common mining services, possibly indicating the infection of a system with a cryptominer.
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This rule monitors for the execution of suspicious linux tools through ProxyChains. ProxyChains is a command-line tool that enables the routing of network connections through intermediary proxies, enhancing anonymity and enabling access to restricted resources. Attackers can exploit the ProxyChains utility to hide their true source IP address, evade detection, and perform malicious activities through a chain of proxy servers, potentially masking their identity and intentions.
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This rule monitors for the usage of the which command with an unusual amount of process arguments. Attackers may leverage the which command to enumerate the system for useful installed utilities that may be used after compromising a system to escalate privileges or move latteraly across the network.
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Identifies the deletion of sensitive Linux system logs. This may indicate an attempt to evade detection or destroy forensic evidence on a system.
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Files that are placed in the /etc/init.d/ directory in Unix can be used to start custom applications, services, scripts or commands during start-up. Init.d has been mostly replaced in favor of Systemd. However, the "systemd-sysv-generator" can convert init.d files to service unit files that run at boot. Adversaries may add or alter files located in the /etc/init.d/ directory to execute malicious code upon boot in order to gain persistence on the system.
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This rule monitors for inter-process communication via Unix sockets. Adversaries may attempt to communicate with local Unix sockets to enumerate application details, find vulnerabilities/configuration mistakes and potentially escalate privileges or set up malicious communication channels via Unix sockets for inter-process communication to attempt to evade detection.
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This rule detects when an unusual child process is spawned from the
dbus-daemonparent process. Thedbus-daemonprocess is a message bus system that provides a way for applications to talk to each other. Attackers may abuse this process to execute malicious code or escalate privileges.
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This rule detects the execution of the
pkexeccommand by a shell process. Thepkexeccommand is used to execute programs as another user, typically as the superuser. Through thenew_termsrule type, unusual executions ofpkexecare identified, and may indicate an attempt to escalate privileges or perform unauthorized actions on the system.
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This rule identifies when a web server is spawned via Python. Attackers may use Python to spawn a web server to exfiltrate/infiltrate data or to move laterally within a network.
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This rule detects the execution of the
grepcommand with thepluginsargument on Linux systems. This command is used to search for YUM/DNF configurations and/or plugins with an enabled state. This behavior may indicate an attacker is attempting to establish persistence in a YUM or DNF plugin.
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This rule detects the use of system search utilities like grep and find to search for AWS credentials inside a container. Unauthorized access to these sensitive files could lead to further compromise of the container environment or facilitate a container breakout to the underlying cloud environment.
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This rule detects when a container management binary is run from inside a container. These binaries are critical components of many containerized environments, and their presence and execution in unauthorized containers could indicate compromise or a misconfiguration.
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This rule detects when chmod is used to add the execute permission to a file inside a container. Modifying file permissions to make a file executable could indicate malicious activity, as an attacker may attempt to run unauthorized or malicious code inside the container.
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This rule detects the use of the built-in Linux DebugFS utility from inside a privileged container. DebugFS is a special file system debugging utility which supports reading and writing directly from a hard drive device. When launched inside a privileged container, a container deployed with all the capabilities of the host machine, an attacker can access sensitive host level files which could be used for further privilege escalation and container escapes to the host machine.
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This rule detects interactive 'exec' events launched against a container using the 'exec' command. Using the 'exec' command in a pod allows a user to establish a temporary shell session and execute any process/command inside the container. This rule specifically targets higher-risk interactive commands that allow real-time interaction with a container's shell. A malicious actor could use this level of access to further compromise the container environment or attempt a container breakout.
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This rule detects the use of the mount utility from inside a privileged container. The mount command is used to make a device or file system accessible to the system, and then to connect its root directory to a specified mount point on the local file system. When launched inside a privileged container--a container deployed with all the capabilities of the host machine-- an attacker can access sensitive host level files which could be used for further privilege escalation and container escapes to the host machine. Any usage of mount inside a running privileged container should be further investigated.
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This rule detects an established netcat listener running inside a container. Netcat is a utility used for reading and writing data across network connections, and it can be used for malicious purposes such as establishing a backdoor for persistence or exfiltrating data.
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This rule detects modification of the cgroup notify_on_release file from inside a container. When the notify_on_release flag is enabled (1) in a cgroup, then whenever the last task in the cgroup exits or attaches to another cgroup, the command specified in the release_agent file is run and invoked from the host. A privileged container with SYS_ADMIN capabilities, enables a threat actor to mount a cgroup directory and modify the notify_on_release flag in order to take advantage of this feature, which could be used for further privilege escalation and container escapes to the host machine.
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This rule detects modification of the CGroup release_agent file from inside a privileged container. The release_agent is a script that is executed at the termination of any process on that CGroup and is invoked from the host. A privileged container with SYS_ADMIN capabilities, enables a threat actor to mount a CGroup directory and modify the release_agent which could be used for further privilege escalation and container escapes to the host machine.
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Identifies the use of a compression utility to collect known files containing sensitive information, such as credentials and system configurations inside a container.
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This rule detects the use of system search utilities like grep and find to search for private SSH keys or passwords inside a container. Unauthorized access to these sensitive files could lead to further compromise of the container environment or facilitate a container breakout to the underlying host machine.
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This rule detects the creation or modification of an authorized_keys or sshd_config file inside a container. The Secure Shell (SSH) authorized_keys file specifies which users are allowed to log into a server using public key authentication. Adversaries may modify it to maintain persistence on a victim host by adding their own public key(s). Unexpected and unauthorized SSH usage inside a container can be an indicator of compromise and should be investigated.
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This rule detects an incoming SSH connection established inside a running container. Running an ssh daemon inside a container should be avoided and monitored closely if necessary. If an attacker gains valid credentials they can use it to gain initial access or establish persistence within a compromised environment.
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This rule detects an SSH or SSHD process executed from inside a container. This includes both the client ssh binary and server ssh daemon process. SSH usage inside a container should be avoided and monitored closely when necessary. With valid credentials an attacker may move laterally to other containers or to the underlying host through container breakout. They may also use valid SSH credentials as a persistence mechanism.
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This rule detects when an interactive shell is spawned inside a running container. This could indicate a potential container breakout attempt or an attacker's attempt to gain unauthorized access to the underlying host.
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This rule detects commonly abused network utilities running inside a container. Network utilities like nc, nmap, dig, tcpdump, ngrep, telnet, mitmproxy, zmap can be used for malicious purposes such as network reconnaissance, monitoring, or exploitation, and should be monitored closely within a container.
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Identifies a potential forced authentication using related SMB named pipes. Attackers may attempt to force targets to authenticate to a host controlled by them to capture hashes or enable relay attacks.
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Identifies suspicious file download activity from a Google Drive URL. This could indicate an attempt to deliver phishing payloads via a trusted webservice.
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Identifies the execution of a binary by root in Linux shared memory directories: (/dev/shm/, /run/shm/, /var/run/, /var/lock/). This activity is to be considered highly abnormal and should be investigated. Threat actors have placed executables used for persistence on high-uptime servers in these directories as system backdoors.
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Users can mark specific files as hidden simply by putting a "." as the first character in the file or folder name. Adversaries can use this to their advantage to hide files and folders on the system for persistence and defense evasion. This rule looks for hidden files or folders in common writable directories.
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This rule detects the use of the
curlcommand-line tool with SOCKS proxy options, launched from an unusual parent process. Attackers may usecurlto establish a SOCKS proxy connection to bypass network restrictions and exfiltrate data or communicate with C2 servers.
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Detects the manual creation of files in specific etc directories, via user root, used by Linux malware to persist and elevate privileges on compromised systems. File creation in these directories should not be entirely common and could indicate a malicious binary or script installing persistence mechanisms for long term access.
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Detects the creation or modification of files related to the dynamic linker on Linux systems. The dynamic linker is a shared library that is used by the Linux kernel to load and execute programs. Attackers may attempt to hijack the execution flow of a program by modifying the dynamic linker configuration files.
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This rule identifies a sequence of events where a process named
entrypoint.shis started in a container, followed by a network connection attempt. This sequence indicates a potential egress connection from an entrypoint in a container. An entrypoint is a command or script specified in the Dockerfile and executed when the container starts. Attackers can use this technique to establish a foothold in the environment, escape from a container to the host, or establish persistence.
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This rule monitors for the creation of a file, followed by its execution and self-deletion in a short timespan within a directory often used for malicious purposes by threat actors. This behavior is often used by malware to execute malicious code and delete itself to hide its tracks.
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This rule detects kernel seeking activity through several built-in Linux utilities. Attackers may use these utilities to search the Linux kernel for available symbols, functions, and other information that can be used to exploit the kernel.
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This rule detects kernel unpacking activity through several built-in Linux utilities. Attackers may use these utilities to unpack kernel images and modules to search for vulnerabilities or to modify the kernel.
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Identifies the abuse of a Linux binary to break out of a restricted shell or environment by spawning an interactive system shell. The activity of spawning a shell from a binary is not common behavior for a user or system administrator, and may indicate an attempt to evade detection, increase capabilities or enhance the stability of an adversary.
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This rule monitors for the execution of the cat command, followed by a connection attempt by the same process. Cat is capable of transfering data via tcp/udp channels by redirecting its read output to a /dev/tcp or /dev/udp channel. This activity is highly suspicious, and should be investigated. Attackers may leverage this capability to transfer tools or files to another host in the network or exfiltrate data while attempting to evade detection in the process.
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This detection rule addresses multiple vulnerabilities in the CUPS printing system, including CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177. Specifically, this rule detects network connections initiated by a child processes of foomatic-rip. These flaws impact components like cups-browsed, libcupsfilters, libppd, and foomatic-rip, allowing remote unauthenticated attackers to manipulate IPP URLs or inject malicious data through crafted UDP packets or network spoofing. This can result in arbitrary command execution when a print job is initiated.
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Monitors for the execution of a unix binary with read, write and execute memory region permissions, followed by a network connection. The mprotect() system call is used to change the access protections on a region of memory that has already been allocated. This syscall allows a process to modify the permissions of pages in its virtual address space, enabling or disabling permissions such as read, write, and execute for those pages. RWX permissions on memory is in many cases overly permissive, and should (especially in conjunction with an outbound network connection) be analyzed thoroughly.
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This rule identifies an egress internet connection initiated by an SSH Daemon child process. This behavior is indicative of the alteration of a shell configuration file or other mechanism that launches a process when a new SSH login occurs. Attackers can also backdoor the SSH daemon to allow for persistence, call out to a C2 or to steal credentials.
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This rule monitors a sequence involving a program compilation event followed by its execution and a subsequent network connection event. This behavior can indicate the set up of a reverse tcp connection to a command-and-control server. Attackers may spawn reverse shells to establish persistence onto a target system.
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Detects network connections initiated by the "sudo" binary. This behavior is uncommon and may occur in instances where reverse shell shellcode is injected into a process run with elevated permissions via "sudo". Attackers may attempt to inject shellcode into processes running as root, to escalate privileges.
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Detects network connections initiated through Cross-Desktop Group (XDG) autostart entries for GNOME and XFCE-based Linux distributions. XDG Autostart entries can be used to execute arbitrary commands or scripts when a user logs in. This rule helps to identify potential malicious activity where an attacker may have modified XDG autostart scripts to establish persistence on the system.
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This rule monitors for suspicious activities that may indicate an attacker attempting to execute arbitrary code within a PostgreSQL environment. Attackers can execute code via PostgreSQL as a result of gaining unauthorized access to a public facing PostgreSQL database or exploiting vulnerabilities, such as remote command execution and SQL injection attacks, which can result in unauthorized access and malicious actions, and facilitate post-exploitation activities for unauthorized access and malicious actions.
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Detects potential exploitation of curl CVE-2023-38545 by monitoring for vulnerable command line arguments in conjunction with an unusual command line length. A flaw in curl version <= 8.3 makes curl vulnerable to a heap based buffer overflow during the SOCKS5 proxy handshake. Upgrade to curl version >= 8.4 to patch this vulnerability. This exploit can be executed with and without the use of environment variables. For increased visibility, enable the collection of http_proxy, HTTPS_PROXY and ALL_PROXY environment variables based on the instructions provided in the setup guide of this rule.
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It identifies potential malicious shell executions through remote SSH and detects cases where the sshd service suddenly terminates soon after successful execution, suggesting suspicious behavior similar to the XZ backdoor.
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Identifies multiple consecutive login attempts executed by one process targeting a local linux user account within a short time interval. Adversaries might brute force login attempts across different users with a default wordlist or a set of customly crafted passwords in an attempt to gain access to these accounts.
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Potential Linux Ransomware Note Creation Detected
This rule identifies a sequence of a mass file encryption event in conjunction with the creation of a .txt file with a file name containing ransomware keywords executed by the same process in a 1 second timespan. Ransomware is a type of malware that encrypts a victim's files or systems and demands payment (usually in cryptocurrency) in exchange for the decryption key. One important indicator of a ransomware attack is the mass encryption of the file system, after which a new file extension is added to the file.
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This rule monitors for the usage of Docker runtime sockets to escalate privileges on Linux systems. Docker sockets by default are only be writable by the root user and docker group. Attackers that have permissions to write to these sockets may be able to create and run a container that allows them to escalate privileges and gain further access onto the host file system.
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This rule monitors for the execution of processes that interact with Linux containers through an interactive shell without root permissions. Utilities such as runc and ctr are universal command-line utilities leveraged to interact with containers via root permissions. On systems where the access to these utilities are misconfigured, attackers might be able to create and run a container that mounts the root folder or spawn a privileged container vulnerable to a container escape attack, which might allow them to escalate privileges and gain further access onto the host file system.
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This rule detects potential privilege escalation attempts through Looney Tunables (CVE-2023-4911). Looney Tunables is a buffer overflow vulnerability in GNU C Library's dynamic loader's processing of the GLIBC_TUNABLES environment variable.
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Identifies an attempt to exploit a local privilege escalation CVE-2022-37706 via a flaw in Linux window manager package Enlightenment. enlightenment_sys in Enlightenment before 0.25.4 allows local users to gain privileges because it is setuid root, and the system library function mishandles pathnames that begin with a /dev/.. substring.
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Identifies an attempt to exploit a local privilege escalation (CVE-2023-2640 and CVE-2023-32629) via a flaw in Ubuntu's modifications to OverlayFS. These flaws allow the creation of specialized executables, which, upon execution, grant the ability to escalate privileges to root on the affected machine.
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This detection rule monitors for the execution of a system command with setuid or setgid capabilities via Python, followed by a uid or gid change to the root user. This sequence of events may indicate successful privilege escalation. Setuid (Set User ID) and setgid (Set Group ID) are Unix-like OS features that enable processes to run with elevated privileges, based on the file owner or group. Threat actors can exploit these attributes to escalate privileges to the privileges that are set on the binary that is being executed.
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This rule monitors a sequence involving a program compilation event followed by its execution and a subsequent alteration of UID permissions to root privileges. This behavior can potentially indicate the execution of a kernel or software privilege escalation exploit.
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This rule monitors for the execution of the systemd-run command by a user with a UID that is larger than the maximum allowed UID size (INT_MAX). Some older Linux versions were affected by a bug which allows user accounts with a UID greater than INT_MAX to escalate privileges by spawning a shell through systemd-run.
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This rule monitors for common command line flags leveraged by the Chisel client utility followed by a connection attempt. Chisel is a command-line utility used for creating and managing TCP and UDP tunnels, enabling port forwarding and secure communication between machines. Attackers can abuse the Chisel utility to establish covert communication channels, bypass network restrictions, and carry out malicious activities by creating tunnels that allow unauthorized access to internal systems.
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This rule monitors for common command line flags leveraged by the Chisel server utility followed by a received connection within a timespan of 1 minute. Chisel is a command-line utility used for creating and managing TCP and UDP tunnels, enabling port forwarding and secure communication between machines. Attackers can abuse the Chisel utility to establish covert communication channels, bypass network restrictions, and carry out malicious activities by creating tunnels that allow unauthorized access to internal systems.
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This detection rule identifies suspicious network traffic patterns associated with TCP reverse shell activity. This activity consists of a parent-child relationship where a network event is followed by the creation of a shell process. An attacker may establish a Linux TCP reverse shell to gain remote access to a target system.
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This detection rule identifies suspicious network traffic patterns associated with TCP reverse shell activity. This activity consists of a network event that is followed by the creation of a shell process with suspicious command line arguments. An attacker may establish a Linux TCP reverse shell to gain remote access to a target system.
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This detection rule identifies the execution of a Linux shell process from a Java JAR application post an incoming network connection. This behavior may indicate reverse shell activity via a Java application.
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This detection rule detects the creation of a shell through a chain consisting of the execution of a suspicious binary (located in a commonly abused location or executed manually) followed by a network event and ending with a shell being spawned. Stageless reverse tcp shells display this behaviour. Attackers may spawn reverse shells to establish persistence onto a target system.
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This detection rule detects the creation of a shell through a suspicious process chain. Any reverse shells spawned by the specified utilities that are initialized from a single process followed by a network connection attempt will be captured through this rule. Attackers may spawn reverse shells to establish persistence onto a target system.
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This rule detects potential sudo token manipulation attacks through process injection by monitoring the use of a debugger (gdb) process followed by a successful uid change event during the execution of the sudo process. A sudo token manipulation attack is performed by injecting into a process that has a valid sudo token, which can then be used by attackers to activate their own sudo token. This attack requires ptrace to be enabled in conjunction with the existence of a living process that has a valid sudo token with the same uid as the current user.
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This rule monitors for the usage of the built-in Linux DebugFS utility to access a disk device without root permissions. Linux users that are part of the "disk" group have sufficient privileges to access all data inside of the machine through DebugFS. Attackers may leverage DebugFS in conjunction with "disk" permissions to read sensitive files owned by root, such as the shadow file, root ssh private keys or other sensitive files that may allow them to further escalate privileges.
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This detection rule addresses multiple vulnerabilities in the CUPS printing system, including CVE-2024-47176, CVE-2024-47076, CVE-2024-47175, and CVE-2024-47177. Specifically, this rule detects shell executions from the foomatic-rip parent process through the default printer user (lp). These flaws impact components like cups-browsed, libcupsfilters, libppd, and foomatic-rip, allowing remote unauthenticated attackers to manipulate IPP URLs or inject malicious data through crafted UDP packets or network spoofing. This can result in arbitrary command execution when a print job is initiated.
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Identifies instances where a processes (granted CAP_CHOWN and/or CAP_FOWNER capabilities) is executed, after which the ownership of a suspicious file or binary is changed. In Linux, the CAP_CHOWN capability allows a process to change the owner of a file, while CAP_FOWNER permits it to bypass permission checks on operations that require file ownership (like reading, writing, and executing). Attackers may abuse these capabilities to obtain unauthorized access to files.
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Identifies instances where a process (granted CAP_SETUID and/or CAP_SETGID capabilities) is executed, after which the user's access is elevated to UID/GID 0 (root). In Linux, the CAP_SETUID and CAP_SETGID capabilities allow a process to change its UID and GID, respectively, providing control over user and group identity management. Attackers may leverage a misconfiguration for exploitation in order to escalate their privileges to root.
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Identifies instances where GDB (granted the CAP_SYS_PTRACE capability) is executed, after which the user's access is elevated to UID/GID 0 (root). In Linux, the CAP_SYS_PTRACE capability grants a process the ability to use the ptrace system call, which is typically used for debugging and allows the process to trace and control other processes. Attackers may leverage this capability to hook and inject into a process that is running with root permissions in order to escalate their privileges to root.
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Identifies instances where a process is executed with user/group ID 0 (root), and a real user/group ID that is not 0. This is indicative of a process that has been granted SUID/SGID permissions, allowing it to run with elevated privileges. Attackers may leverage a misconfiguration for exploitation in order to escalate their privileges to root, or establish a backdoor for persistence.
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Identifies recursive process capability enumeration of the entire filesystem through the getcap command. Malicious users may manipulate identified capabilities to gain root privileges.
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Identifies a new process starting from a process ID (PID), lock or reboot file within the temporary file storage paradigm (tmpfs) directory /var/run directory. On Linux, the PID files typically hold the process ID to track previous copies running and manage other tasks. Certain Linux malware use the /var/run directory for holding data, executables and other tasks, disguising itself or these files as legitimate PID files.
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This rule monitors the creation/alteration of the rc.local/rc.common file. The /etc/rc.local file is used to start custom applications, services, scripts or commands during start-up. The rc.local file has mostly been replaced by Systemd. However, through the "systemd-rc-local-generator", rc.local files can be converted to services that run at boot. Adversaries may alter rc.local/rc.common to execute malicious code at start-up, and gain persistence onto the system.
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Identifies instances where GDB (granted the CAP_SYS_PTRACE capability) is executed, after which an outbound network connection is initiated by UID/GID 0 (root). In Linux, the CAP_SYS_PTRACE capability grants a process the ability to use the ptrace system call, which is typically used for debugging and allows the process to trace and control other processes. Attackers may leverage this capability to hook and inject into a process that is running with root permissions in order to execute shell code and gain a reverse shell with root privileges.
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This rule monitors for the usage of the "find" command in conjunction with SUID and SGUID permission arguments. SUID (Set User ID) and SGID (Set Group ID) are special permissions in Linux that allow a program to execute with the privileges of the file owner or group, respectively, rather than the privileges of the user running the program. In case an attacker is able to enumerate and find a binary that is misconfigured, they might be able to leverage this misconfiguration to escalate privileges by exploiting vulnerabilities or built-in features in the privileged program.
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Monitors for /proc//maps file reads. The /proc//maps file in Linux provides a memory map for a specific process, detailing the memory segments, permissions, and what files are mapped to these segments. Attackers may read a process's memory map to identify memory addresses for code injection or process hijacking.
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Detects suspicious network events executed by the APT package manager, potentially indicating persistence through an APT backdoor. In Linux, APT (Advanced Package Tool) is a command-line utility used for handling packages on Debian-based systems, providing functions for installing, updating, upgrading, and removing software along with managing package repositories. Attackers can backdoor APT to gain persistence by injecting malicious code into scripts that APT runs, thereby ensuring continued unauthorized access or control each time APT is used for package management.
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Suspicious Data Encryption via OpenSSL Utility
Identifies when the openssl command-line utility is used to encrypt multiple files on a host within a short time window. Adversaries may encrypt data on a single or multiple systems in order to disrupt the availability of their target's data and may attempt to hold the organization's data to ransom for the purposes of extortion.
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Monitors for the elevation of regular user permissions to root permissions through the kworker process. kworker, or kernel worker, processes are part of the kernel's workqueue mechanism. They are responsible for executing work that has been scheduled to be done in kernel space, which might include tasks like handling interrupts, background activities, and other kernel-related tasks. Attackers may attempt to evade detection by masquerading as a kernel worker process, and hijack the execution flow by hooking certain functions/syscalls through a rootkit in order to provide easy access to root via a special modified command.
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Detects suspicious network events executed by systemd, potentially indicating persistence through a systemd backdoor. Systemd is a system and service manager for Linux operating systems, used to initialize and manage system processes. Attackers can backdoor systemd for persistence by creating or modifying systemd unit files to execute malicious scripts or commands, or by replacing legitimate systemd binaries with compromised ones, ensuring that their malicious code is automatically executed at system startup or during certain system events.
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Monitors for the generation of a passwd password entry via openssl, followed by a file write activity on the "/etc/passwd" file. The "/etc/passwd" file in Linux stores user account information, including usernames, user IDs, group IDs, home directories, and default shell paths. Attackers may exploit a misconfiguration in the "/etc/passwd" file permissions or other privileges to add a new entry to the "/etc/passwd" file with root permissions, and leverage this new user account to login as root.
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Identifies instances where VMware-related files, such as those with extensions like ".vmdk", ".vmx", ".vmxf", ".vmsd", ".vmsn", ".vswp", ".vmss", ".nvram", and ".vmem", are renamed on a Linux system. The rule monitors for the "rename" event action associated with these file types, which could indicate malicious activity.
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Identifies instances where the "index.html" file within the "/usr/lib/vmware/*" directory is renamed on a Linux system. The rule monitors for the "rename" event action associated with this specific file and path, which could indicate malicious activity.
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Identifies the creation of a symbolic link to a suspicious file or location. A symbolic link is a reference to a file or directory that acts as a pointer or shortcut, allowing users to access the target file or directory from a different location in the file system. An attacker can potentially leverage symbolic links for privilege escalation by tricking a privileged process into following the symbolic link to a sensitive file, giving the attacker access to data or capabilities they would not normally have.
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Identifies instances where VMware processes, such as "vmware-vmx" or "vmx," are terminated on a Linux system by a "kill" command. The rule monitors for the "end" event type, which signifies the termination of a process. The presence of a "kill" command as the parent process for terminating VMware processes may indicate that a threat actor is attempting to interfere with the virtualized environment on the targeted system.
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This rule identifies file permission modification events on files located in common system binary paths. Adversaries may attempt to hide their payloads in the default Linux system directories, and modify the file permissions of these payloads prior to execution.
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This rule detects the execution of the DPKG command by processes not associated with the DPKG package manager. The DPKG command is used to install, remove, and manage Debian packages on a Linux system. Attackers can abuse the DPKG command to install malicious packages on a system.
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This rule identifies potentially malicious processes attempting to access the cloud service provider's instance metadata service (IMDS) API endpoint, which can be used to retrieve sensitive instance-specific information such as instance ID, public IP address, and even temporary security credentials if role's are assumed by that instance. The rule monitors for various tools and scripts like curl, wget, python, and perl that might be used to interact with the metadata API.
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This rule monitors for a sequence of 20 "id" command executions within 1 second by the same parent process. This behavior is unusual, and may be indicative of the execution of an enumeration script such as LinPEAS or LinEnum. These scripts leverage the "id" command to enumerate the privileges of all users present on the system.
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This rule monitors for (ana)cron jobs being created or renamed. Linux cron jobs are scheduled tasks that can be leveraged by system administrators to set up scheduled tasks, but may be abused by malicious actors for persistence, privilege escalation and command execution. By creating or modifying cron job configurations, attackers can execute malicious commands or scripts at predefined intervals, ensuring their continued presence and enabling unauthorized activities.
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Linux Group Creation
Identifies attempts to create a new group. Attackers may create new groups to establish persistence on a system.
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Linux User Account Creation
Identifies attempts to create new users. Attackers may add new users to establish persistence on a system.
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This rule detects the creation of potentially malicious files within the default MOTD file directories. Message of the day (MOTD) is the message that is presented to the user when a user connects to a Linux server via SSH or a serial connection. Linux systems contain several default MOTD files located in the "/etc/update-motd.d/" directory. These scripts run as the root user every time a user connects over SSH or a serial connection. Adversaries may create malicious MOTD files that grant them persistence onto the target every time a user connects to the system by executing a backdoor script or command.
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Adversaries may modify SSH related binaries for persistence or credential access by patching sensitive functions to enable unauthorized access or by logging SSH credentials for exfiltration.
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This rule monitors for network connectivity to the internet from a previously unknown executable located in a suspicious directory. An alert from this rule can indicate the presence of potentially malicious activity, such as the execution of unauthorized or suspicious processes attempting to establish connections to unknown or suspicious destinations such as a command and control server. Detecting and investigating such behavior can help identify and mitigate potential security threats, protecting the system and its data from potential compromise.
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This rule detects the creation or renaming of a new Systemd file in all of the common Systemd service locations for both root and regular users. Systemd service files are configuration files in Linux systems used to define and manage system services. Malicious actors can leverage systemd service files to achieve persistence by creating or modifying services to execute malicious commands or payloads during system startup or at a predefined interval by adding a systemd timer. This allows them to maintain unauthorized access, execute additional malicious activities, or evade detection.
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Systemctl is a process used in Linux systems to manage systemd processes through service configuration files. Malicious actors can leverage systemd services to achieve persistence by creating or modifying service files to execute malicious commands or payloads during system startup. This allows them to maintain unauthorized access, execute additional malicious activities, or evade detection.
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Detects the creation of a systemd timer within any of the default systemd timer directories. Systemd timers can be used by an attacker to gain persistence, by scheduling the execution of a command or script. Similarly to cron/at, systemd timers can be set up to execute on boot time, or on a specific point in time, which allows attackers to regain access in case the connection to the infected asset was lost.
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Identifies modification of the dynamic linker preload shared object (ld.so.preload). Adversaries may execute malicious payloads by hijacking the dynamic linker used to load libraries.
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Identifies an outbound network connection by JAVA to LDAP, RMI or DNS standard ports followed by a suspicious JAVA child processes. This may indicate an attempt to exploit a JAVA/NDI (Java Naming and Directory Interface) injection vulnerability.
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Identifies potential privilege escalation exploitation of DAC (Discretionary access control) file permissions. The rule identifies exploitation of DAC checks on sensitive file paths via suspicious processes whose capabilities include CAP_DAC_OVERRIDE (where a process can bypass all read write and execution checks) or CAP_DAC_READ_SEARCH (where a process can read any file or perform any executable permission on the directories).
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Monitors for the elevation of regular user permissions to root permissions through a previously unknown executable. Attackers may attempt to evade detection by hijacking the execution flow and hooking certain functions/syscalls through a rootkit in order to provide easy access to root via a special modified command.
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This rule monitors for Linux Shadow file modifications. These modifications are indicative of a potential password change or user addition event. Threat actors may attempt to create new users or change the password of a user account to maintain access to a system.
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This rule monitors the creation/alteration of a shell configuration file. Unix systems use shell configuration files to set environment variables, create aliases, and customize the user's environment. Adversaries may modify or add a shell configuration file to execute malicious code and gain persistence in the system. This behavior is consistent with the Kaiji malware family.
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This rule detects the creation of a systemd generator file. Generators are small executables executed by systemd at bootup and during configuration reloads. Their main role is to convert non-native configuration and execution parameters into dynamically generated unit files, symlinks, or drop-ins, extending the unit file hierarchy for the service manager. Systemd generators can be used to execute arbitrary code at boot time, which can be leveraged by attackers to maintain persistence on a Linux system.
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Monitors for the creation of rule files that are used by systemd-udevd to manage device nodes and handle kernel device events in the Linux operating system. Systemd-udevd can be exploited for persistence by adversaries by creating malicious udev rules that trigger on specific events, executing arbitrary commands or payloads whenever a certain device is plugged in or recognized by the system.
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This rule detects the creation of an unusual SSHD child process through the usage of the
new_termsrule type. Attackers may abuse SSH to maintain persistence on a compromised system, or to establish a backdoor for remote access, potentially resulting in an unusual SSHD child process being created.
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This rule leverages the
auditd_managerintegration to detect user or group creation or modification events on Linux systems. Threat actors may attempt to create or modify users or groups to establish persistence on the system.
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Detects file creation events in the plugin directories for the Yum package manager. In Linux, Yum (Yellowdog Updater, Modified) is a command-line utility used for handling packages on (by default) Fedora-based systems, providing functions for installing, updating, upgrading, and removing software along with managing package repositories. Attackers can backdoor Yum to gain persistence by injecting malicious code into plugins that Yum runs, thereby ensuring continued unauthorized access or control each time Yum is used for package management.
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Detects file creation events in the configuration directory for the APT package manager. In Linux, APT (Advanced Package Tool) is a command-line utility used for handling packages on (by default) Debian-based systems, providing functions for installing, updating, upgrading, and removing software along with managing package repositories. Attackers can backdoor APT to gain persistence by injecting malicious code into scripts that APT runs, thereby ensuring continued unauthorized access or control each time APT is used for package management.
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This rule detects the creation of a Linux kernel object file (.ko) on a system. Threat actors may leverage Linux kernel object files to load a rootkit or other type of malware on a system providing them with complete control and the ability to hide from security products.
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Identifies the creation of a Process ID (PID), lock or reboot file created in temporary file storage paradigm (tmpfs) directory /var/run. On Linux, the PID files typically hold the process ID to track previous copies running and manage other tasks. Certain Linux malware use the /var/run directory for holding data, executables and other tasks, disguising itself or these files as legitimate PID files.
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This rule detects the execution of a PATH variable in a command line invocation by a shell process. This behavior is unusual and may indicate an attempt to execute a command from a non-standard location. This technique may be used to evade detection or perform unauthorized actions on the system.
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Monitors for the execution of a previously unknown unix binary with read, write and execute memory region permissions. The mprotect() system call is used to change the access protections on a region of memory that has already been allocated. This syscall allows a process to modify the permissions of pages in its virtual address space, enabling or disabling permissions such as read, write, and execute for those pages. RWX permissions on memory is in many cases overly permissive, and should be analyzed thoroughly.
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Suspicious Usage of bpf_probe_write_user Helper
This rule monitors the syslog log file for messages related to instances of a program using the
bpf_probe_write_userhelper. Thebpf_probe_write_userhelper is used to write data to user space from a BPF program. Unauthorized use of this helper can be indicative of an eBPF rootkit or other malicious activity.
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Loadable Kernel Modules (or LKMs) are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. This identifies attempts to enumerate information about a kernel module.
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Identifies file permission modifications in common writable directories by a non-root user. Adversaries often drop files or payloads into a writable directory and change permissions prior to execution.
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Potential Pspy Process Monitoring Detected
This rule leverages auditd to monitor for processes scanning different processes within the /proc directory using the openat syscall. This is a strong indication for the usage of the pspy utility. Attackers may leverage the pspy process monitoring utility to monitor system processes without requiring root permissions, in order to find potential privilege escalation vectors.
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This rule detects the creation or renaming of the SELinux configuration file. SELinux is a security module that provides access control security policies. Modifications to the SELinux configuration file may indicate an attempt to impair defenses by disabling or modifying security tools.
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This rule detects interactive shells launched from system users. System users typically do not require interactive shells, and their presence may indicate malicious activity.
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This rule monitors for network connections from a kworker process. kworker, or kernel worker, processes are part of the kernel's workqueue mechanism. They are responsible for executing work that has been scheduled to be done in kernel space, which might include tasks like handling interrupts, background activities, and other kernel-related tasks. Attackers may attempt to evade detection by masquerading as a kernel worker process.
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This rule monitors for the copying or moving of a system binary. Adversaries may copy/move and rename system binaries to evade detection. Copying a system binary to a different location should not occur often, so if it does, the activity should be investigated.
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Process Started with Executable Stack
This rule monitors the syslog log file for messages related to instances of processes that are started with an executable stack. This can be an indicator of a process that is attempting to execute code from the stack, which can be a security risk.
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This rule detects the execution of shell commands by systemd during the boot process on Linux systems. Systemd is a system and service manager for Linux operating systems. Attackers may execute shell commands during the boot process to maintain persistence on the system. This may be a sign of malicious systemd services, initramfs or GRUB bootloader manipulation, or other persistence mechanisms.
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Looks for compiler activity by a user context which does not normally run compilers. This can be the result of ad-hoc software changes or unauthorized software deployment. This can also be due to local privilege elevation via locally run exploits or malware activity.
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This rule monitors for at jobs being created or renamed. Linux at jobs are scheduled tasks that can be leveraged by system administrators to set up scheduled tasks, but may be abused by malicious actors for persistence, privilege escalation and command execution. By creating or modifying cron job configurations, attackers can execute malicious commands or scripts at predefined intervals, ensuring their continued presence and enabling unauthorized activities.
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This rule detects successful authentications via PAM grantors that are not commonly used. This could indicate an attacker is attempting to escalate privileges or maintain persistence on the system by modifying the default PAM configuration.
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Detects the use of the AWS CLI with the
--endpoint-urlargument, which allows users to specify a custom endpoint URL for AWS services. This can be leveraged by adversaries to redirect API requests to non-standard or malicious endpoints, potentially bypassing typical security controls and logging mechanisms. This behavior may indicate an attempt to interact with unauthorized or compromised infrastructure, exfiltrate data, or perform other malicious activities under the guise of legitimate AWS operations.
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Identifies the use of the AWS Systems Manager (SSM)
SendCommandAPI with the eitherAWS-RunShellScriptorAWS-RunPowerShellScriptparameters. TheSendCommandAPI call allows users to execute commands on EC2 instances using the SSM service. Adversaries may use this technique to execute commands on EC2 instances without the need for SSH or RDP access. This behavior may indicate an adversary attempting to execute commands on an EC2 instance for malicious purposes. This is a New Terms rule that only flags when this behavior is observed for the first time on a host in the last 7 days.
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Both ~/.bash_profile and ~/.bashrc are files containing shell commands that are run when Bash is invoked. These files are executed in a user's context, either interactively or non-interactively, when a user logs in so that their environment is set correctly. Adversaries may abuse this to establish persistence by executing malicious content triggered by a user’s shell.
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This rule monitors for the creation or modification of Pluggable Authentication Module (PAM) shared object files or configuration files. Attackers may create or modify these files to maintain persistence on a compromised system, or harvest account credentials.
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This rule identifies a UID change event via
nsenter. Thensentercommand is used to enter a namespace, which is a way to isolate processes and resources. Attackers can usensenterto escape from a container to the host, which can lead to privilege escalation and lateral movement.
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DPKG Package Installed by Unusual Parent Process
This rule detects the installation of a Debian package (dpkg) by an unusual parent process. The dpkg command is used to install, remove, and manage Debian packages on a Linux system. Attackers can abuse the dpkg command to install malicious packages on a system.
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Identifies the execution of and EggShell Backdoor. EggShell is a known post exploitation tool for macOS and Linux.
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Identifies the Elastic endpoint agent has stopped and is no longer running on the host. Adversaries may attempt to disable security monitoring tools in an attempt to evade detection or prevention capabilities during an intrusion. This may also indicate an issue with the agent itself and should be addressed to ensure defensive measures are back in a stable state.
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This rule detects a suspicious egress network connection attempt from a Git hook script. Git hooks are scripts that Git executes before or after events such as: commit, push, and receive. An attacker can abuse these features to execute arbitrary commands on the system, establish persistence or to initialize a network connection to a remote server and exfiltrate data or download additional payloads.
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Identifies when a terminal (tty) is spawned via Perl. Attackers may upgrade a simple reverse shell to a fully interactive tty after obtaining initial access to a host.
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Detects the loading of a Linux kernel module through system calls. Threat actors may leverage Linux kernel modules to load a rootkit on a system providing them with complete control and the ability to hide from security products. As other rules monitor for the addition of Linux kernel modules through system utilities or .ko files, this rule covers the gap that evasive rootkits leverage by monitoring for kernel module additions on the lowest level through auditd_manager.
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Detects the loading of a Linux kernel module by a non-root user through system calls. Threat actors may leverage Linux kernel modules to load a rootkit on a system providing them with complete control and the ability to hide from security products. As other rules monitor for the addition of Linux kernel modules through system utilities or .ko files, this rule covers the gap that evasive rootkits leverage by monitoring for kernel module additions on the lowest level through auditd_manager.
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This rule monitors for the usage of the most common clipboard utilities on unix systems by an uncommon process group leader. Adversaries may collect data stored in the clipboard from users copying information within or between applications.
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This rule detects the creation of Loadable Kernel Module (LKM) configuration files. Attackers may create or modify these files to allow their LKMs to be loaded upon reboot, ensuring persistence on a compromised system.
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This rule identifies successful logins by system users that are uncommon to authenticate. These users have
nologinset by default, and must be modified to allow SSH access. Adversaries may backdoor these users to gain unauthorized access to the system.
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This rules identifies a process created from an executable with a space appended to the end of the filename. This may indicate an attempt to masquerade a malicious file as benign to gain user execution. When a space is added to the end of certain files, the OS will execute the file according to it's true filetype instead of it's extension. Adversaries can hide a program's true filetype by changing the extension of the file. They can then add a space to the end of the name so that the OS automatically executes the file when it's double-clicked.
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Adversaries may modify the standard authentication module for persistence via patching the normal authorization process or modifying the login configuration to allow unauthorized access or elevate privileges.
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This rule detects the usage of
curlorwgetto download the source code of a Pluggable Authentication Module (PAM) shared object file. Attackers may download the source code of a PAM shared object file to create a backdoor in the authentication process.
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Detects potential buffer overflow attacks by querying the "Segfault Detected" pre-built rule signal index, through a threshold rule, with a minimum number of 100 segfault alerts in a short timespan. A large amount of segfaults in a short time interval could indicate application exploitation attempts.
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Potential Execution of rc.local Script
This rule detects the potential execution of the
/etc/rc.localscript through thealready_runningevent action created by therc-local.servicesystemd service. The/etc/rc.localscript is a legacy initialization script that is executed at the end of the boot process. The/etc/rc.localscript is not enabled by default on most Linux distributions. The/etc/rc.localscript can be used by attackers to persistently execute malicious commands or scripts on a compromised system at reboot. As the rc.local file is executed prior to the initialization of Elastic Defend, the execution event is not ingested, and therefore thealready_runningevent is leveraged to provide insight into the potential execution ofrc.local.
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Potential External Linux SSH Brute Force Detected
Identifies multiple external consecutive login failures targeting a user account from the same source address within a short time interval. Adversaries will often brute force login attempts across multiple users with a common or known password, in an attempt to gain access to these accounts.
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Potential Internal Linux SSH Brute Force Detected
Identifies multiple internal consecutive login failures targeting a user account from the same source address within a short time interval. Adversaries will often brute force login attempts across multiple users with a common or known password, in an attempt to gain access to these accounts.
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Potential Meterpreter Reverse Shell
This detection rule identifies a sample of suspicious Linux system file reads used for system fingerprinting, leveraged by the Metasploit Meterpreter shell to gather information about the target that it is executing its shell on. Detecting this pattern is indicative of a successful meterpreter shell connection.
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This threshold rule monitors for the rapid execution of unix utilities that are capable of conducting network scans. Adversaries may leverage built-in tools such as ping, netcat or socat to execute ping sweeps across the network while attempting to evade detection or due to the lack of network mapping tools available on the compromised host.
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Identifies potentially malicious processes communicating via a port paring typically not associated with SSH. For example, SSH over port 2200 or port 2222 as opposed to the traditional port 22. Adversaries may make changes to the standard port a protocol uses to bypass filtering or muddle analysis/parsing of network data.
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This rule leverages the File Integrity Monitoring (FIM) integration to detect file modifications of files that are commonly used for persistence on Linux systems. The rule detects modifications to files that are commonly used for cron jobs, systemd services, message-of-the-day (MOTD), SSH configurations, shell configurations, runtime control, init daemon, passwd/sudoers/shadow files, Systemd udevd, and XDG/KDE autostart entries. To leverage this rule, the paths specified in the query need to be added to the FIM policy in the Elastic Security app.
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A sudoers file specifies the commands users or groups can run and from which terminals. Adversaries can take advantage of these configurations to execute commands as other users or spawn processes with higher privileges.
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This rule leverages Auditd data to detect the use of the
prctlsyscall to potentially hide a process by changing its name. Theprctlsyscall is used to control various process attributes. Attackers can use this syscall to change the name of a process to a hidden directory or file, making it harder to detect. The query looks for theprctlsyscall with thePR_SET_NAMEargument set tof(PR_SET_NAME is used to set the name of a process).
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Potential Reverse Shell via UDP
This detection rule identifies suspicious network traffic patterns associated with UDP reverse shell activity. This activity consists of a sample of an execve, socket and connect syscall executed by the same process, where the auditd.data.a0-1 indicate a UDP connection, ending with an egress connection event. An attacker may establish a Linux UDP reverse shell to bypass traditional firewall restrictions and gain remote access to a target system covertly.
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Identifies access to the /etc/shadow file via the commandline using standard system utilities. After elevating privileges to root, threat actors may attempt to read or dump this file in order to gain valid credentials. They may utilize these to move laterally undetected and access additional resources.
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An FTP (file transfer protocol) brute force attack is a method where an attacker systematically tries different combinations of usernames and passwords to gain unauthorized access to an FTP server, and if successful, the impact can include unauthorized data access, manipulation, or theft, compromising the security and integrity of the server and potentially exposing sensitive information. This rule identifies multiple consecutive authentication failures targeting a specific user account from the same source address and within a short time interval, followed by a successful authentication.
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An RDP (Remote Desktop Protocol) brute force attack involves an attacker repeatedly attempting various username and password combinations to gain unauthorized access to a remote computer via RDP, and if successful, the potential impact can include unauthorized control over the compromised system, data theft, or the ability to launch further attacks within the network, jeopardizing the security and confidentiality of the targeted system and potentially compromising the entire network infrastructure. This rule identifies multiple consecutive authentication failures targeting a specific user account within a short time interval, followed by a successful authentication.
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Potential Successful SSH Brute Force Attack
Identifies multiple SSH login failures followed by a successful one from the same source address. Adversaries can attempt to login into multiple users with a common or known password to gain access to accounts.
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Identifies the creation of a sudo binary located at /usr/bin/sudo. Attackers may hijack the default sudo binary and replace it with a custom binary or script that can read the user's password in clear text to escalate privileges or enable persistence onto the system every time the sudo binary is executed.
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This rule leverages the new_terms rule type to identify the creation of a potentially unsafe docker container from an unusual parent process. Attackers can use the
--privilegedflag to create containers with escalated privileges, which can lead to trivial privilege escalation, docker escaping and persistence. access.
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RPM Package Installed by Unusual Parent Process
This rule leverages the new_terms rule type to identify the installation of RPM packages by an unusual parent process. RPM is a package management system used in Linux systems such as Red Hat, CentOS and Fedora. Attacks may backdoor RPM packages to gain initial access or install malicious RPM packages to maintain persistence.
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Identifies the use of a compression utility to collect known files containing sensitive information, such as credentials and system configurations.
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This rule detects connections accepted by a simple HTTP web server in Python and PHP built-in modules. Adversaries may create simple HTTP web servers to establish persistence on a compromised system by uploading a reverse or command shell payload to the server web root, allowing them to regain remote access to the system if lost. This event may occur when an attacker requests the server to execute a command or script via a potential backdoor.
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The Secure Shell (SSH) authorized_keys file specifies which users are allowed to log into a server using public key authentication. Adversaries may modify it to maintain persistence on a victim host by adding their own public key(s).
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Identifies the attempted use of a heap-based buffer overflow vulnerability for the Sudo binary in Unix-like systems (CVE-2021-3156). Successful exploitation allows an unprivileged user to escalate to the root user.
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A sudoers file specifies the commands that users or groups can run and from which terminals. Adversaries can take advantage of these configurations to execute commands as other users or spawn processes with higher privileges.
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An adversary may add the setuid or setgid bit to a file or directory in order to run a file with the privileges of the owning user or group. An adversary can take advantage of this to either do a shell escape or exploit a vulnerability in an application with the setuid or setgid bit to get code running in a different user’s context. Additionally, adversaries can use this mechanism on their own malware to make sure they're able to execute in elevated contexts in the future.
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Suspicious rc.local Error Message
This rule monitors the syslog log file for error messages related to the rc.local process. The rc.local file is a script that is executed during the boot process on Linux systems. Attackers may attempt to modify the rc.local file to execute malicious commands or scripts during system startup. This rule detects error messages such as "Connection refused," "No such file or directory," or "command not found" in the syslog log file, which may indicate that the rc.local file has been tampered with.
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This rule monitors for the execution of several commonly used system commands executed by a previously unknown executable located in commonly abused directories. An alert from this rule can indicate the presence of potentially malicious activity, such as the execution of unauthorized or suspicious processes attempting to run malicious code. Detecting and investigating such behavior can help identify and mitigate potential security threats, protecting the system and its data from potential compromise.
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Tainted Kernel Module Load
This rule monitors the syslog log file for messages related to instances of a tainted kernel module load. Rootkits often leverage kernel modules as their main defense evasion technique. Detecting tainted kernel module loads is crucial for ensuring system security and integrity, as malicious or unauthorized modules can compromise the kernel and lead to system vulnerabilities or unauthorized access.
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Tainted Out-Of-Tree Kernel Module Load
This rule monitors the syslog log file for messages related to instances of a out-of-tree kernel module load, indicating the taining of the kernel. Rootkits often leverage kernel modules as their main defense evasion technique. Detecting tainted kernel module loads is crucial for ensuring system security and integrity, as malicious or unauthorized modules can compromise the kernel and lead to system vulnerabilities or unauthorized access.
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Adversaries may attempt to clear or disable the Bash command-line history in an attempt to evade detection or forensic investigations.
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Timestomping is an anti-forensics technique which is used to modify the timestamps of a file, often to mimic files that are in the same folder.
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Unusual Linux Network Activity
Identifies Linux processes that do not usually use the network but have unexpected network activity, which can indicate command-and-control, lateral movement, persistence, or data exfiltration activity. A process with unusual network activity can denote process exploitation or injection, where the process is used to run persistence mechanisms that allow a malicious actor remote access or control of the host, data exfiltration, and execution of unauthorized network applications.
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Looks for commands related to system network configuration discovery from an unusual user context. This can be due to uncommon troubleshooting activity or due to a compromised account. A compromised account may be used by a threat actor to engage in system network configuration discovery in order to increase their understanding of connected networks and hosts. This information may be used to shape follow-up behaviors such as lateral movement or additional discovery.
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Looks for commands related to system network connection discovery from an unusual user context. This can be due to uncommon troubleshooting activity or due to a compromised account. A compromised account may be used by a threat actor to engage in system network connection discovery in order to increase their understanding of connected services and systems. This information may be used to shape follow-up behaviors such as lateral movement or additional discovery.
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Unusual Linux Network Port Activity
Identifies unusual destination port activity that can indicate command-and-control, persistence mechanism, or data exfiltration activity. Rarely used destination port activity is generally unusual in Linux fleets, and can indicate unauthorized access or threat actor activity.
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Looks for anomalous access to the metadata service by an unusual process. The metadata service may be targeted in order to harvest credentials or user data scripts containing secrets.
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Looks for commands related to system process discovery from an unusual user context. This can be due to uncommon troubleshooting activity or due to a compromised account. A compromised account may be used by a threat actor to engage in system process discovery in order to increase their understanding of software applications running on a target host or network. This may be a precursor to selection of a persistence mechanism or a method of privilege elevation.
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Looks for commands related to system information discovery from an unusual user context. This can be due to uncommon troubleshooting activity or due to a compromised account. A compromised account may be used to engage in system information discovery in order to gather detailed information about system configuration and software versions. This may be a precursor to selection of a persistence mechanism or a method of privilege elevation.
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Looks for anomalous access to the cloud platform metadata service by an unusual user. The metadata service may be targeted in order to harvest credentials or user data scripts containing secrets.
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Looks for commands related to system user or owner discovery from an unusual user context. This can be due to uncommon troubleshooting activity or due to a compromised account. A compromised account may be used to engage in system owner or user discovery in order to identify currently active or primary users of a system. This may be a precursor to additional discovery, credential dumping or privilege elevation activity.
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A machine learning job detected activity for a username that is not normally active, which can indicate unauthorized changes, activity by unauthorized users, lateral movement, or compromised credentials. In many organizations, new usernames are not often created apart from specific types of system activities, such as creating new accounts for new employees. These user accounts quickly become active and routine. Events from rarely used usernames can point to suspicious activity. Additionally, automated Linux fleets tend to see activity from rarely used usernames only when personnel log in to make authorized or unauthorized changes, or threat actors have acquired credentials and log in for malicious purposes. Unusual usernames can also indicate pivoting, where compromised credentials are used to try and move laterally from one host to another.
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This rule detects processes that are executed with environment variables that are not commonly used. This could indicate an attacker is attempting to hijack the execution flow of a process by loading malicious libraries or binaries into the process memory space.
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Identifies rare processes that do not usually run on individual hosts, which can indicate execution of unauthorized services, malware, or persistence mechanisms. Processes are considered rare when they only run occasionally as compared with other processes running on the host.
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Looks for sudo activity from an unusual user context. An unusual sudo user could be due to troubleshooting activity or it could be a sign of credentialed access via compromised accounts.
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An adversary may attempt to get detailed information about the operating system and hardware. This rule identifies common locations used to discover virtual machine hardware by a non-root user. This technique has been used by the Pupy RAT and other malware.
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An adversary may attempt to get detailed information about the operating system and hardware. This rule identifies common locations used to discover virtual machine hardware by a non-root user. This technique has been used by the Pupy RAT and other malware.
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Identifies suspicious child processes of the Java interpreter process. This may indicate an attempt to execute a malicious JAR file or an exploitation attempt via a JAVA specific vulnerability.
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Identifies the use of the grep command to discover known third-party macOS and Linux security tools, such as Antivirus or Host Firewall details.
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Identifies the execution of a shell process with suspicious arguments which may be indicative of reverse shell activity.
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Suspicious File Changes Activity Detected
This rule identifies a sequence of 100 file extension rename events within a set of common file paths by the same process in a timespan of 1 second. Ransomware is a type of malware that encrypts a victim's files or systems and demands payment (usually in cryptocurrency) in exchange for the decryption key. One important indicator of a ransomware attack is the mass encryption of the file system, after which a new file extension is added to the file.
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Searches for rare processes running on multiple Linux hosts in an entire fleet or network. This reduces the detection of false positives since automated maintenance processes usually only run occasionally on a single machine but are common to all or many hosts in a fleet.
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This rule identifies a high number (10) of process terminations via pkill from the same host within a short time period.
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Potential Linux Reverse Connection through Port Knocking
Monitors for a sequence of network activity on atypical ports, prior to receiving a single packet on such a non-standard port, which potentially indicates signal port knocking activity. Port knocking is a covert method of externally opening ports by sending a sequence of packets to previously closed ports, which adversaries may leverage to discreetly gain access without directly alerting traditional monitoring systems.
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Deprecated - Potential Reverse Shell via Suspicious Parent Process
This detection rule detects the creation of a shell through a suspicious parent child relationship. Any reverse shells spawned by the specified utilities that use a forked process to initialize the connection attempt will be captured through this rule. Attackers may spawn reverse shells to establish persistence onto a target system.
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Iodine is a tool for tunneling Internet protocol version 4 (IPV4) traffic over the DNS protocol to circumvent firewalls, network security groups, and network access lists while evading detection.
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This rule detects the execution of a process where the LD_PRELOAD environment variable is set. LD_PRELOAD can be used to inject a shared library into a binary at or prior to execution. A threat actor may do this in order to load a malicious shared library for the purposes of persistence, privilege escalation, and defense evasion. This activity is not common and will potentially indicate malicious or suspicious behavior.
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Suspicious Network Connection Attempt by Root
Identifies an outbound network connection attempt followed by a session id change as the root user by the same process entity. This particular instantiation of a network connection is abnormal and should be investigated as it may indicate a potential reverse shell activity via a privileged process.
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Potential SSH Brute Force Detected on Privileged Account
Identifies multiple consecutive login failures targeting a root user account from the same source address and within a short time interval. Adversaries will often brute force login attempts on privileged accounts with a common or known password, in an attempt to gain privileged access to systems.
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Reverse Shell Created via Named Pipe
Identifies a reverse shell via the abuse of named pipes on Linux with the help of OpenSSL or Netcat. First in, first out (FIFO) files are special files for reading and writing to by Linux processes. For this to work, a named pipe is created and passed to a Linux shell where the use of a network connection tool such as Netcat or OpenSSL has been established. The stdout and stderr are captured in the named pipe from the network connection and passed back to the shell for execution.
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