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Suspicious Execution via Windows Subsystem for Linux

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Suspicious Execution via Windows Subsystem for Linux

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Detects Linux Bash commands from the the Windows Subsystem for Linux. Adversaries may enable and use WSL for Linux to avoid detection.

Rule type: eql

Rule indices:

winlogbeat-*
logs-endpoint.events.process-*
logs-windows.sysmon_operational-*
endgame-*
logs-m365_defender.event-*
logs-sentinel_one_cloud_funnel.*

Severity: low

Risk score: 21

Runs every: 5m

Searches indices from: now-9m (Date Math format, see also Additional look-back time)

Maximum alerts per execution: 100

References:

Tags:

Domain: Endpoint
OS: Windows
Use Case: Threat Detection
Tactic: Execution
Tactic: Defense Evasion
Data Source: Elastic Endgame
Data Source: Elastic Defend
Data Source: Microsoft Defender for Endpoint
Data Source: Sysmon
Data Source: SentinelOne

Version: 107

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

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process where host.os.type == "windows" and event.type : "start" and
  (
    (
      (process.executable : "?:\\Windows\\System32\\bash.exe" or ?process.pe.original_file_name == "Bash.exe") and
      not process.command_line : ("bash", "bash.exe")
    ) or
    process.executable : "?:\\Users\\*\\AppData\\Local\\Packages\\*\\rootfs\\usr\\bin\\bash" or
    (
      process.parent.name : "wsl.exe" and process.parent.command_line : "bash*" and not process.name : "wslhost.exe"
    ) or
    (
      process.name : "wsl.exe" and process.args : (
        "curl", "/etc/shadow", "/etc/passwd", "cat", "--system", "root", "-e", "--exec", "bash", "/mnt/c/*"
      ) and not process.args : ("wsl-bootstrap", "docker-desktop-data", "*.vscode-server*")
    )
  ) and
    not process.parent.executable : ("?:\\Program Files\\Docker\\*.exe", "?:\\Program Files (x86)\\Docker\\*.exe")

Framework: MITRE ATT&CK^TM

Tactic:
- Name: Defense Evasion
- ID: TA0005
- Reference URL: https://attack.mitre.org/tactics/TA0005/
Technique:
- Name: Indirect Command Execution
- ID: T1202
- Reference URL: https://attack.mitre.org/techniques/T1202/
Tactic:
- Name: Execution
- ID: TA0002
- Reference URL: https://attack.mitre.org/tactics/TA0002/
Technique:
- Name: Command and Scripting Interpreter
- ID: T1059
- Reference URL: https://attack.mitre.org/techniques/T1059/
Sub-technique:
- Name: Unix Shell
- ID: T1059.004
- Reference URL: https://attack.mitre.org/techniques/T1059/004/

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