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Potential Script Proxy Execution Via CL_Mutexverifiers.ps1

SIGMA detection rule by Nasreddine Bencherchali (Nextron Systems), oscd.community, Natalia Shornikova, frack113 · NOASSERTION

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

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.stealth
    - 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

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

ab3f9e02-97bf-4c28-8ddd-d47d656036a2

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

[[ reason ]]

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Format & documentation suggestions

Not a security issue — this rule is valid and was accepted as-is. These are optional fields/conventions its own format recommends, mainly affecting its quality score and how well it documents itself for other reviewers.

[[ reason ]]

What do these messages mean?

[[ currentRule.title && currentRule.title.length > 60 ? currentRule.title.slice(0, 60) + '…' : currentRule.title ]]

[[ currentRule.title ]]

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