Suspicious Process Spawned from MOTD Detected

  1[metadata]
  2creation_date = "2023/02/28"
  3integration = ["endpoint"]
  4maturity = "production"
  5min_stack_comments = "New fields added: required_fields, related_integrations, setup"
  6min_stack_version = "8.3.0"
  7updated_date = "2024/02/21"
  8
  9[transform]
 10[[transform.osquery]]
 11label = "Osquery - Retrieve File Information"
 12query = "SELECT * FROM file WHERE path = {{file.path}}"
 13
 14[[transform.osquery]]
 15label = "Osquery - Retrieve File Listing Information"
 16query = "SELECT * FROM file WHERE (path LIKE '/etc/update-motd.d/%' OR path LIKE '/usr/lib/update-notifier/%')"
 17
 18[[transform.osquery]]
 19label = "Osquery - Retrieve Additional File Listing Information"
 20query = """
 21SELECT
 22  f.path,
 23  u.username AS file_owner,
 24  g.groupname AS group_owner,
 25  datetime(f.atime, 'unixepoch') AS file_last_access_time,
 26  datetime(f.mtime, 'unixepoch') AS file_last_modified_time,
 27  datetime(f.ctime, 'unixepoch') AS file_last_status_change_time,
 28  datetime(f.btime, 'unixepoch') AS file_created_time,
 29  f.size AS size_bytes
 30FROM
 31  file f
 32  LEFT JOIN users u ON f.uid = u.uid
 33  LEFT JOIN groups g ON f.gid = g.gid
 34WHERE (path LIKE '/etc/update-motd.d/%' OR path LIKE '/usr/lib/update-notifier/%')
 35"""
 36
 37[[transform.osquery]]
 38label = "Osquery - Retrieve Running Processes by User"
 39query = "SELECT pid, username, name FROM processes p JOIN users u ON u.uid = p.uid ORDER BY username"
 40
 41[[transform.osquery]]
 42label = "Osquery - Retrieve Crontab Information"
 43query = "SELECT * FROM crontab"
 44[rule]
 45author = ["Elastic"]
 46description = """
 47Message of the day (MOTD) is the message that is presented to the user when a user connects to a Linux server via SSH 
 48or a serial connection. Linux systems contain several default MOTD files located in the "/etc/update-motd.d/" and 
 49"/usr/lib/update-notifier/" directories. These scripts run as the root user every time a user connects over SSH or a 
 50serial connection. Adversaries may create malicious MOTD files that grant them persistence onto the target every time a 
 51user connects to the system by executing a backdoor script or command. This rule detects the execution of potentially 
 52malicious processes through the MOTD utility. 
 53"""
 54from = "now-9m"
 55index = ["logs-endpoint.events.*", "endgame-*"]
 56language = "eql"
 57license = "Elastic License v2"
 58name = "Suspicious Process Spawned from MOTD Detected"
 59note = """## Triage and analysis
 60
 61### Investigating Suspicious Process Spawned from MOTD Detected
 62
 63The message-of-the-day (MOTD) is used to display a customizable system-wide message or information to users upon login in Linux.
 64
 65Attackers can abuse message-of-the-day (motd) files to run scripts, commands or malicious software every time a user connects to a system over SSH or a serial connection, by creating a new file within the `/etc/update-motd.d/` or `/usr/lib/update-notifier/` directory. Files in these directories will automatically run with root privileges when they are made executable.
 66
 67This rule identifies the execution of potentially malicious processes from a MOTD script, which is not likely to occur as default benign behavior. 
 68
 69> **Note**:
 70> This investigation guide uses the [Osquery Markdown Plugin](https://www.elastic.co/guide/en/security/master/invest-guide-run-osquery.html) introduced in Elastic Stack version 8.5.0. Older Elastic Stack versions will display unrendered Markdown in this guide.
 71> 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.
 72
 73#### Possible Investigation Steps
 74
 75- Investigate the file that was created or modified from which the suspicious process was executed.
 76  - $osquery_0
 77- Investigate whether any other files in the `/etc/update-motd.d/` or `/usr/lib/update-notifier/` directories have been altered.
 78  - $osquery_1
 79  - $osquery_2
 80- 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.
 81  - $osquery_3
 82- Investigate other alerts associated with the user/host during the past 48 hours.
 83- Investigate whether the altered scripts call other malicious scripts elsewhere on the file system. 
 84  - If scripts or executables were dropped, retrieve the files and determine if they are malicious:
 85    - Use a private sandboxed malware analysis system to perform analysis.
 86      - Observe and collect information about the following activities:
 87        - Attempts to contact external domains and addresses.
 88          - Check if the domain is newly registered or unexpected.
 89          - Check the reputation of the domain or IP address.
 90        - File access, modification, and creation activities.
 91        - Cron jobs, services, and other persistence mechanisms.
 92            - $osquery_4
 93
 94### Related Rules
 95
 96- Potential Persistence Through MOTD File Creation Detected - 96d11d31-9a79-480f-8401-da28b194608f
 97
 98### False positive analysis
 99
100- This activity is unlikely to happen legitimately. Any activity that triggered the alert and is not inherently malicious must be monitored by the security team.
101
102### Response and remediation
103
104- Initiate the incident response process based on the outcome of the triage.
105- Isolate the involved host to prevent further post-compromise behavior.
106- If the triage identified malware, search the environment for additional compromised hosts.
107  - Implement temporary network rules, procedures, and segmentation to contain the malware.
108  - Stop suspicious processes.
109  - Immediately block the identified indicators of compromise (IoCs).
110  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
111- 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.
112- Delete the MOTD files or restore them to the original configuration.
113- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
114- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
115- Leverage the incident response data and logging to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
116"""
117references = [
118    "https://pberba.github.io/security/2022/02/06/linux-threat-hunting-for-persistence-initialization-scripts-and-shell-configuration/#10-boot-or-logon-initialization-scripts-motd"
119]
120risk_score = 73
121rule_id = "4ec47004-b34a-42e6-8003-376a123ea447"
122setup = """## Setup
123
124This rule requires data coming in from Elastic Defend.
125
126### Elastic Defend Integration Setup
127Elastic Defend is integrated into the Elastic Agent using Fleet. Upon configuration, the integration allows the Elastic Agent to monitor events on your host and send data to the Elastic Security app.
128
129#### Prerequisite Requirements:
130- Fleet is required for Elastic Defend.
131- To configure Fleet Server refer to the [documentation](https://www.elastic.co/guide/en/fleet/current/fleet-server.html).
132
133#### The following steps should be executed in order to add the Elastic Defend integration on a Linux System:
134- Go to the Kibana home page and click "Add integrations".
135- In the query bar, search for "Elastic Defend" and select the integration to see more details about it.
136- Click "Add Elastic Defend".
137- Configure the integration name and optionally add a description.
138- Select the type of environment you want to protect, either "Traditional Endpoints" or "Cloud Workloads".
139- 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).
140- We suggest selecting "Complete EDR (Endpoint Detection and Response)" as a configuration setting, that provides "All events; all preventions"
141- 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.
142For more details on Elastic Agent configuration settings, refer to the [helper guide](https://www.elastic.co/guide/en/fleet/8.10/agent-policy.html).
143- Click "Save and Continue".
144- 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.
145For more details on Elastic Defend refer to the [helper guide](https://www.elastic.co/guide/en/security/current/install-endpoint.html).
146"""
147severity = "high"
148tags = [
149        "Domain: Endpoint",
150        "OS: Linux",
151        "Use Case: Threat Detection",
152        "Tactic: Persistence",
153        "Data Source: Elastic Endgame",
154        "Resources: Investigation Guide",
155        "Data Source: Elastic Defend"
156        ]
157timestamp_override = "event.ingested"
158type = "eql"
159query = '''
160process where event.type == "start" and event.action : ("exec", "exec_event") and
161process.parent.executable : ("/etc/update-motd.d/*", "/usr/lib/update-notifier/*") and (
162  (process.name in ("bash", "dash", "sh", "tcsh", "csh", "zsh", "ksh", "fish") and (
163    (process.args : ("-i", "-l")) or (process.parent.name == "socat" and process.parent.args : "*exec*"))) or
164  (process.name : ("nc", "ncat", "netcat", "nc.openbsd") and process.args_count >= 3 and 
165    not process.args : ("-*z*", "-*l*")) or
166  (process.name : "python*" and process.args : "-c" and process.args : (
167     "*import*pty*spawn*", "*import*subprocess*call*"
168  )) or
169  (process.name : "perl*" and process.args : "-e" and process.args : "*socket*" and process.args : (
170     "*exec*", "*system*"
171  )) or
172  (process.name : "ruby*" and process.args : ("-e", "-rsocket") and process.args : (
173     "*TCPSocket.new*", "*TCPSocket.open*"
174  )) or
175  (process.name : "lua*" and process.args : "-e" and process.args : "*socket.tcp*" and process.args : (
176     "*io.popen*", "*os.execute*"
177  )) or
178  (process.name : "php*" and process.args : "-r" and process.args : "*fsockopen*" and process.args : "*/bin/*sh*") or 
179  (process.name : ("awk", "gawk", "mawk", "nawk") and process.args : "*/inet/tcp/*") or 
180  (process.name in ("openssl", "telnet"))
181) and 
182not (
183  (process.parent.args : "--force") or
184  (process.args : ("/usr/games/lolcat", "/usr/bin/screenfetch")) or
185  (process.parent.name == "system-crash-notification")
186)
187'''
188
189[[rule.threat]]
190framework = "MITRE ATT&CK"
191
192[[rule.threat.technique]]
193id = "T1037"
194name = "Boot or Logon Initialization Scripts"
195reference = "https://attack.mitre.org/techniques/T1037/"
196
197[rule.threat.tactic]
198id = "TA0003"
199name = "Persistence"
200reference = "https://attack.mitre.org/tactics/TA0003/"