Suspicious Execution via Windows Subsystem for Linux

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.*
endgame-*
logs-system.security*

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: System

Version: 7

Rule authors:

Elastic

Rule license: Elastic License v2

Rule query

edit

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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