Sigma rule: Potential Script Proxy Execution Via CL_Mutexverifiers.ps1

Rule

Title

Potential Script Proxy Execution Via CL_Mutexverifiers.ps1

Status

test

Level

medium

Author

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

Date

2022-05-21

Modified

2023-08-17

File

rules/windows/process_creation/proc_creation_win_powershell_cl_mutexverifiers.yml

Commit

ccbb0369507f796db0b0ae6854c8a2be471b9d84

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

Log source

product

windows

category

process_creation

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_*

False positives (as the rule lists them)

• Unknown

Tags

• attack.stealth
• attack.t1216

MITRE ATT&CK ids this rule names

• T1216

References

• https://lolbas-project.github.io/lolbas/Scripts/CL_mutexverifiers/

Read on 2026-11-03T00:58:21.399Z under licence sigma-drl-1.1@d5f4c36a from https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_powershell_cl_mutexverifiers.yml