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sigmamediumHunting

Potential Script Proxy Execution Via CL_Mutexverifiers.ps1

Detects the use of the Microsoft signed script "CL_mutexverifiers" to proxy the execution of additional PowerShell script commands

MITRE ATT&CK

T1216
defense-evasion

Detection Query

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_*

Author

Nasreddine Bencherchali (Nextron Systems), oscd.community, Natalia Shornikova, frack113

Created

2022-05-21

Data Sources

windowsProcess Creation Events

Platforms

windows

References

Tags

attack.defense-evasionattack.t1216
Raw Content
title: Potential Script Proxy Execution Via CL_Mutexverifiers.ps1
id: 1e0e1a81-e79b-44bc-935b-ddb9c8006b3d
status: test
description: Detects the use of the Microsoft signed script "CL_mutexverifiers" to proxy the execution of additional PowerShell script commands
references:
    - https://lolbas-project.github.io/lolbas/Scripts/CL_mutexverifiers/
author: Nasreddine Bencherchali (Nextron Systems), oscd.community, Natalia Shornikova, frack113
date: 2022-05-21
modified: 2023-08-17
tags:
    - attack.defense-evasion
    - attack.t1216
logsource:
    category: process_creation
    product: windows
detection:
    selection_pwsh:
        ParentImage|endswith:
            # Note: to avoid potential FPs we assume the script was launched from powershell. But in theory it can be launched by any Powershell like process
            - '\powershell.exe'
            - '\pwsh.exe'
        Image|endswith: '\powershell.exe'
        CommandLine|contains: ' -nologo -windowstyle minimized -file '
    selection_temp:
        # Note: Since the function uses "env:temp" the value will change depending on the context of exec
        CommandLine|contains:
            - '\AppData\Local\Temp\'
            - '\Windows\Temp\'
    condition: all of selection_*
falsepositives:
    - Unknown
level: medium