COM Hijacking via TreatAs — Sigma Rule

Rule metadata and linked tags

Author: frack113. Source status: test; severity: medium. Source dates: 2022-08-28 / 2025-07-11.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 3fe904bd9433b488847a69e767b3840ef925637c7d80571183120a9239cddc74

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: COM Hijacking via TreatAs
id: dc5c24af-6995-49b2-86eb-a9ff62199e82
status: test
description: Detect modification of TreatAs key to enable "rundll32.exe -sta" command
references:
    - https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1546.015/T1546.015.md
    - https://www.youtube.com/watch?v=3gz1QmiMhss&t=1251s
author: frack113
date: 2022-08-28
modified: 2025-07-11
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.t1546.015
logsource:
    category: registry_set
    product: windows
detection:
    selection:
        TargetObject|endswith: 'TreatAs\(Default)'
    filter_office:
        Image|startswith: 'C:\Program Files\Common Files\Microsoft Shared\ClickToRun\'
        Image|endswith: '\OfficeClickToRun.exe'
    filter_office2:
        Image:
            - 'C:\Program Files\Microsoft Office\root\integration\integrator.exe'
            - 'C:\Program Files (x86)\Microsoft Office\root\integration\integrator.exe'
    filter_svchost:
        # Example of target object by svchost
        # TargetObject: HKLM\SOFTWARE\Microsoft\MsixRegistryCompatibility\Package\Microsoft.Paint_11.2208.6.0_x64__8wekyb3d8bbwe\User\SOFTWARE\Classes\CLSID\{0003000A-0000-0000-C000-000000000046}\TreatAs\(Default)
        # TargetObject: HKU\S-1-5-21-1000000000-000000000-000000000-0000_Classes\CLSID\{0003000A-0000-0000-C000-000000000046}\TreatAs\(Default)
        Image: 'C:\Windows\system32\svchost.exe'
    filter_misexec:
        # This FP has been seen during installation/updates
        Image:
            - 'C:\Windows\system32\msiexec.exe'
            - 'C:\Windows\SysWOW64\msiexec.exe'
    condition: selection and not 1 of filter_*
falsepositives:
    - Legitimate use
level: medium

Original YAML and metadata in JSON

False positives

• Legitimate use

Source references

• https://github.com/redcanaryco/atomic-red-team/blob/40b77d63808dd4f4eafb83949805636735a1fd15/atomics/T1546.015/T1546.015.md
• https://www.youtube.com/watch?v=3gz1QmiMhss&t=1251s