Windows PowerShell Script Proxy Execution via CL_mutexverifiers.ps1

title: Windows PowerShell Script Proxy Execution via CL_mutexverifiers.ps1
id: c5ba371e-2a28-407f-a31d-6f56b9285242
status: test
description: This rule flags process creation where a signed PowerShell script named CL_mutexverifiers is invoked to proxy execution of additional PowerShell script commands. Attackers can use this kind of script wrapper to stealthily launch secondary PowerShell payloads through an approved, signed script. The detection relies on process creation telemetry capturing the parent PowerShell invocation, the executed PowerShell image, and command-line arguments indicating the wrapped script and temporary path usage.
references:
  - https://lolbas-project.github.io/lolbas/Scripts/CL_mutexverifiers/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_powershell_cl_mutexverifiers.yml
author: Nasreddine Bencherchali (Nextron Systems), oscd.community, Natalia Shornikova, frack113, Huntrule Team
date: 2022-05-21
modified: 2023-08-17
tags:
  - attack.stealth
  - attack.t1216
logsource:
  category: process_creation
  product: windows
detection:
  selection_pwsh:
    ParentImage|endswith:
      - \powershell.exe
      - \pwsh.exe
    Image|endswith: \powershell.exe
    CommandLine|contains: " -nologo -windowstyle minimized -file "
  selection_temp:
    CommandLine|contains:
      - \AppData\Local\Temp\
      - \Windows\Temp\
  condition: all of selection_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 1e0e1a81-e79b-44bc-935b-ddb9c8006b3d
    type: derived