Suspicious Network Activity to the Internet by Previously Unknown Executable

  1[metadata]
  2creation_date = "2023/06/14"
  3integration = ["endpoint"]
  4maturity = "production"
  5updated_date = "2026/09/18"
  6[transform]
  7[[transform.osquery]]
  8label = "Osquery - Retrieve Listening Ports"
  9query = "SELECT pid, address, port, socket, protocol, path FROM listening_ports"
 10
 11[[transform.osquery]]
 12label = "Osquery - Retrieve Open Sockets"
 13query = "SELECT pid, family, remote_address, remote_port, socket, state FROM process_open_sockets"
 14
 15[[transform.osquery]]
 16label = "Osquery - Retrieve Information for a Specific User"
 17query = "SELECT * FROM users WHERE username = {{user.name}}"
 18
 19[[transform.osquery]]
 20label = "Osquery - Investigate the Account Authentication Status"
 21query = "SELECT * FROM logged_in_users WHERE user = {{user.name}}"
 22
 23[[transform.osquery]]
 24label = "Osquery - Retrieve Running Processes by User"
 25query = "SELECT pid, username, name FROM processes p JOIN users u ON u.uid = p.uid ORDER BY username"
 26
 27[[transform.osquery]]
 28label = "Osquery - Retrieve Process Info"
 29query = "SELECT name, cmdline, parent, path, uid FROM processes"
 30
 31
 32[rule]
 33author = ["Elastic"]
 34description = """
 35This rule monitors for network connectivity to the internet from a previously unknown executable located in a suspicious
 36directory. An alert from this rule can indicate the presence of potentially malicious activity, such as the execution of
 37unauthorized or suspicious processes attempting to establish connections to unknown or suspicious destinations such as a
 38command and control server. Detecting and investigating such behavior can help identify and mitigate potential security
 39threats, protecting the system and its data from potential compromise.
 40"""
 41from = "now-59m"
 42index = ["auditbeat-*", "filebeat-*", "packetbeat-*", "logs-endpoint.events.*", "endgame-*"]
 43language = "kuery"
 44license = "Elastic License v2"
 45name = "Suspicious Network Activity to the Internet by Previously Unknown Executable"
 46note = """## Triage and analysis
 47
 48### Investigating Suspicious Network Activity to the Internet by Previously Unknown Executable
 49
 50After being installed, malware will often call out to its command and control server to receive further instructions by its operators.
 51
 52This rule leverages the new terms rule type to detect previously unknown processes, initiating network connections to external IP-addresses. 
 53
 54> **Note**:
 55> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/current/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 56> This investigation guide uses [placeholder fields](https://www.elastic.co/guide/en/security/current/osquery-placeholder-fields.html) to dynamically pass alert data into Osquery queries. Placeholder fields were introduced in Elastic Stack version 8.7.0. If you're using Elastic Stack version 8.6.0 or earlier, you'll need to manually adjust this investigation guide's queries to ensure they properly run.
 57
 58#### Possible investigation steps
 59
 60- Identify any signs of suspicious network activity or anomalies that may indicate malicious behavior. This could include unexpected traffic patterns or unusual network behavior.
 61  - Investigate listening ports and open sockets to look for potential malicious processes, reverse shells or data exfiltration.
 62    - $osquery_0
 63    - $osquery_1
 64- Identify the user account that performed the action, analyze it, and check whether it should perform this kind of action.
 65  - $osquery_2
 66- Investigate whether the user is currently logged in and active.
 67  - $osquery_3
 68- Investigate the script execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence and whether they are located in expected locations.
 69  - $osquery_4
 70  - $osquery_5
 71- Investigate other alerts associated with the user/host during the past 48 hours.
 72  - If scripts or executables were dropped, retrieve the files and determine if they are malicious:
 73    - Use a private sandboxed malware analysis system to perform analysis.
 74      - Observe and collect information about the following activities:
 75        - Attempts to contact external domains and addresses.
 76          - Check if the domain is newly registered or unexpected.
 77          - Check the reputation of the domain or IP address.
 78        - File access, modification, and creation activities.
 79
 80### Related rules
 81
 82- Network Activity Detected via cat - afd04601-12fc-4149-9b78-9c3f8fe45d39
 83
 84### False positive analysis
 85
 86- If this activity is related to new benign software installation activity, consider adding exceptions — preferably with a combination of user and command line conditions.
 87- Try to understand the context of the execution by thinking about the user, machine, or business purpose. A small number of endpoints, such as servers with unique software, might appear unusual but satisfy a specific business need.
 88
 89### Response and remediation
 90
 91- Initiate the incident response process based on the outcome of the triage.
 92- Isolate the involved host to prevent further post-compromise behavior.
 93- If the triage identified malware, search the environment for additional compromised hosts.
 94  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 95  - Stop suspicious processes.
 96  - Immediately block the identified indicators of compromise (IoCs).
 97  - Inspect the affected systems for additional malware backdoors, such as reverse shells, reverse proxies, or droppers, that attackers could use to reinfect the system.
 98- Remove and block malicious artifacts identified during triage.
 99- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
100- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
101- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
102- Leverage the incident response data and logging to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
103"""
104risk_score = 21
105rule_id = "53617418-17b4-4e9c-8a2c-8deb8086ca4b"
106setup = """## Setup
107
108This rule requires data coming in from one of the following integrations:
109- Elastic Defend
110- Auditbeat
111- Filebeat
112- Packetbeat
113
114
115### Elastic Defend Integration Setup
116Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows
117the Elastic Agent to monitor events on your host and send data to the Elastic Security app.
118
119#### Prerequisite Requirements:
120- Fleet is required for Elastic Defend.
121- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).
122
123#### The following steps should be executed in order to add the Elastic Defend integration on a Linux System:
124- Go to the Kibana home page and click "Add integrations".
125- In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
126- Click "Add Elastic Defend".
127- Configure the integration name and optionally add a description.
128- Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
129- Select a configuration preset. Each preset comes with different default settings for Elastic Agent, you can further customize these later by configuring the Elastic Defend integration policy. [Helper guide](https://www.elastic.co/guide/en/security/current/configure-endpoint-integration-policy.html).
130- We suggest to select "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
131- Enter a name for the agent policy in "New agent policy name". If other agent policies already exist, you can click the "Existing hosts" tab and select an existing policy instead.
132For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/8.10/agent-policy.html).
133- Click "Save and Continue".
134- To complete the integration, select "Add Elastic Agent to your hosts" and continue to the next section to install the Elastic Agent on your hosts.
135For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).
136
137### Auditbeat Setup
138Auditbeat is a lightweight shipper that you can install on your servers to audit the activities of users and processes on your systems. For example, you can use Auditbeat to collect and centralize audit events from the Linux Audit Framework. You can also use Auditbeat to detect changes to critical files, like binaries and configuration files, and identify potential security policy violations.
139
140#### The following steps should be executed in order to add the Auditbeat on a Linux System:
141- Elastic provides repositories available for APT and YUM-based distributions. Note that we provide binary packages, but no source packages.
142- To install the APT and YUM repositories follow the setup instructions in this [helper guide](https://www.elastic.co/guide/en/beats/auditbeat/current/setup-repositories.html).
143- To run Auditbeat on Docker follow the setup instructions in the [helper guide](https://www.elastic.co/guide/en/beats/auditbeat/current/running-on-docker.html).
144- To run Auditbeat on Kubernetes follow the setup instructions in the [helper guide](https://www.elastic.co/guide/en/beats/auditbeat/current/running-on-kubernetes.html).
145- For complete “Setup and Run Auditbeat” information refer to the [helper guide](https://www.elastic.co/guide/en/beats/auditbeat/current/setting-up-and-running.html).
146
147### Filebeat Setup
148Filebeat is a lightweight shipper for forwarding and centralizing log data. Installed as an agent on your servers, Filebeat monitors the log files or locations that you specify, collects log events, and forwards them either to Elasticsearch or Logstash for indexing.
149
150#### The following steps should be executed in order to add the Filebeat on a Linux System:
151- Elastic provides repositories available for APT and YUM-based distributions. Note that we provide binary packages, but no source packages.
152- To install the APT and YUM repositories follow the setup instructions in this [helper guide](https://www.elastic.co/guide/en/beats/filebeat/current/setup-repositories.html).
153- To run Filebeat on Docker follow the setup instructions in the [helper guide](https://www.elastic.co/guide/en/beats/filebeat/current/running-on-docker.html).
154- To run Filebeat on Kubernetes follow the setup instructions in the [helper guide](https://www.elastic.co/guide/en/beats/filebeat/current/running-on-kubernetes.html).
155- For quick start information for Filebeat refer to the [helper guide](https://www.elastic.co/guide/en/beats/filebeat/8.11/filebeat-installation-configuration.html).
156- For complete “Setup and Run Filebeat” information refer to the [helper guide](https://www.elastic.co/guide/en/beats/filebeat/current/setting-up-and-running.html).
157
158### Packetbeat Setup
159Packetbeat is a real-time network packet analyzer that you can use for application monitoring, performance analytics, and threat detection. Packetbeat works by capturing the network traffic between your application servers, decoding the application layer protocols (HTTP, MySQL, Redis, and so on), correlating the requests with the responses, and recording the interesting fields for each transaction.
160
161#### The following steps should be executed in order to add the Packetbeat on a  Linux System:
162- Elastic provides repositories available for APT and YUM-based distributions. Note that we provide binary packages, but no source packages.
163- To install the APT and YUM repositories follow the setup instructions in this [helper guide](https://www.elastic.co/guide/en/beats/packetbeat/current/setup-repositories.html).
164- To run Packetbeat on Docker follow the setup instructions in the [helper guide](https://www.elastic.co/guide/en/beats/packetbeat/current/running-on-docker.html).
165- For quick start information for Packetbeat refer to the [helper guide](https://www.elastic.co/guide/en/beats/packetbeat/current/packetbeat-installation-configuration.html).
166- For complete “Setup and Run Packetbeat” information refer to the [helper guide](https://www.elastic.co/guide/en/beats/packetbeat/current/setting-up-and-running.html).
167"""
168severity = "low"
169tags = [
170    "Domain: Endpoint",
171    "OS: Linux",
172    "Use Case: Threat Detection",
173    "Tactic: Command and Control",
174    "Data Source: Elastic Endgame",
175    "Data Source: Elastic Defend",
176    "Resources: Investigation Guide",
177    "Noise: Low",
178    "Performance: Normal",
179    "Rule Type: New Terms",
180    "Platform: Linux",
181    "Data Source: Network Packet Capture",
182    "Resources: Osquery",
183]
184timestamp_override = "event.ingested"
185type = "new_terms"
186
187query = '''
188host.os.type:linux and event.category:network and event.action:(connection_attempted or ipv4_connection_attempt_event) and
189process.executable : (
190  /etc/crontab or /etc/rc.local or ./* or /boot/* or /dev/shm/* or /etc/cron.*/* or /etc/init.d/* or /etc/rc*.d/* or
191  /etc/update-motd.d/* or /home/*/.* or /tmp/* or /usr/lib/update-notifier/* or /var/log/* or /var/tmp/*
192) and process.name : * and
193not (
194  process.executable : (
195    /tmp/newroot/* or /tmp/snap.rootfs* or /etc/cron.hourly/BitdefenderRedline or /tmp/go-build* or /srv/snp/docker/* or
196    /run/containerd/* or /tmp/.mount* or /run/k3s/containerd/* or /tmp/selenium* or /tmp/tmp.*/juliainstaller or
197    /tmp/.criu.mntns* or /home/*/.local/share/containers/* or /etc/update-motd.d/*
198  ) or
199  source.ip:(10.0.0.0/8 or 127.0.0.0/8 or 172.16.0.0/12 or 192.168.0.0/16) or
200  process.name : (
201    apt or chrome or curl or dnf or dockerd or dpkg or firefox-bin or git-remote-https or java or kite-update or
202    kited or node or rpm or saml2aws or selenium-manager or solana-validator or wget or yum or ansible* or aws* or
203    php* or pip* or python* or steam* or terraform* or filebeat or apk or cursor or http
204  ) or
205  destination.ip:(
206    0.0.0.0 or 10.0.0.0/8 or 100.64.0.0/10 or 127.0.0.0/8 or 169.254.0.0/16 or 172.16.0.0/12 or 192.0.0.0/24 or
207    192.0.0.0/29 or 192.0.0.10/32 or 192.0.0.170/32 or 192.0.0.171/32 or 192.0.0.8/32 or 192.0.0.9/32 or 192.0.2.0/24 or
208    192.168.0.0/16 or 192.175.48.0/24 or 192.31.196.0/24 or 192.52.193.0/24 or 192.88.99.0/24 or 198.18.0.0/15 or
209    198.51.100.0/24 or 203.0.113.0/24 or 224.0.0.0/4 or 240.0.0.0/4 or "::1" or "FE80::/10" or "FF00::/8"
210  )
211)
212'''
213
214[[rule.threat]]
215framework = "MITRE ATT&CK"
216
217[[rule.threat.technique]]
218id = "T1071"
219name = "Application Layer Protocol"
220reference = "https://attack.mitre.org/techniques/T1071/"
221
222[rule.threat.tactic]
223id = "TA0011"
224name = "Command and Control"
225reference = "https://attack.mitre.org/tactics/TA0011/"
226
227[[rule.threat]]
228framework = "MITRE ATT&CK"
229
230[[rule.threat.technique]]
231id = "T1037"
232name = "Boot or Logon Initialization Scripts"
233reference = "https://attack.mitre.org/techniques/T1037/"
234
235[[rule.threat.technique.subtechnique]]
236id = "T1037.004"
237name = "RC Scripts"
238reference = "https://attack.mitre.org/techniques/T1037/004/"
239
240[[rule.threat.technique]]
241id = "T1053"
242name = "Scheduled Task/Job"
243reference = "https://attack.mitre.org/techniques/T1053/"
244
245[[rule.threat.technique.subtechnique]]
246id = "T1053.003"
247name = "Cron"
248reference = "https://attack.mitre.org/techniques/T1053/003/"
249
250[rule.threat.tactic]
251id = "TA0003"
252name = "Persistence"
253reference = "https://attack.mitre.org/tactics/TA0003/"
254[rule.new_terms]
255field = "new_terms_fields"
256value = ["process.executable"]
257
258[[rule.new_terms.history_window_start]]
259field = "history_window_start"
260value = "now-20d"