Potential Suspicious Mofcomp Execution — Sigma Rule

Rule metadata and linked tags

Author: Nasreddine Bencherchali (Nextron Systems). Source status: test; severity: high. Source dates: 2022-07-12 / 2023-04-11.

{
  "category": "process_creation",
  "product": "windows"
}

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: bd46719d891e2496bbc5f2b416ee7ba9659ac2026aa842a1b9d12e5c05a45046

Detection logic

Original source YAML. Source-tag agreement is not proof of complete semantic coverage. This rule has not been compiled for a SIEM backend or validated against live telemetry here.

title: Potential Suspicious Mofcomp Execution
id: 1dd05363-104e-4b4a-b963-196a534b03a1
status: test
description: |
    Detects execution of the "mofcomp" utility as a child of a suspicious shell or script running utility or by having a suspicious path in the commandline.
    The "mofcomp" utility parses a file containing MOF statements and adds the classes and class instances defined in the file to the WMI repository.
    Attackers abuse this utility to install malicious MOF scripts
references:
    - https://thedfirreport.com/2022/07/11/select-xmrig-from-sqlserver/
    - https://github.com/The-DFIR-Report/Sigma-Rules/blob/75260568a7ffe61b2458ca05f6f25914efb44337/win_mofcomp_execution.yml
    - https://learn.microsoft.com/en-us/windows/win32/wmisdk/mofcomp
author: Nasreddine Bencherchali (Nextron Systems)
date: 2022-07-12
modified: 2023-04-11
tags:
    - attack.stealth
    - attack.t1218
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\mofcomp.exe'
        - OriginalFileName: 'mofcomp.exe'
    selection_case:
        - ParentImage|endswith:
              - '\cmd.exe'
              - '\powershell.exe'
              - '\pwsh.exe'
              - '\wsl.exe'
              - '\wscript.exe'
              - '\cscript.exe'
        - CommandLine|contains:
              - '\AppData\Local\Temp'
              - '\Users\Public\'
              - '\WINDOWS\Temp\'
              - '%temp%'
              - '%tmp%'
              - '%appdata%'
    filter_main_wmiprvse:
        ParentImage: 'C:\Windows\System32\wbem\WmiPrvSE.exe'
        CommandLine|contains: 'C:\Windows\TEMP\'
        CommandLine|endswith: '.mof'
    filter_optional_null_parent:
        # Sometimes the parent information isn't available from the Microsoft-Windows-Security-Auditing provider.
        CommandLine|contains: 'C:\Windows\TEMP\'
        CommandLine|endswith: '.mof'
    condition: all of selection_* and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: high

Original YAML and metadata in JSON

False positives

• Unknown

Source references

• https://thedfirreport.com/2022/07/11/select-xmrig-from-sqlserver/
• https://github.com/The-DFIR-Report/Sigma-Rules/blob/75260568a7ffe61b2458ca05f6f25914efb44337/win_mofcomp_execution.yml
• https://learn.microsoft.com/en-us/windows/win32/wmisdk/mofcomp