Bypass UAC via CMSTP — Sigma Rule

Rule metadata and linked tags

Author: E.M. Anhaus (originally from Atomic Blue Detections, Endgame), oscd.community. Source status: test; severity: high. Source dates: 2019-10-24 / 2022-08-30.

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

Pinned original Sigma rule · Detection Rule License 1.1

Source SHA-256: 6c28b33446b35b40892f9a2612ba1d938b5030300075df79037ffbf5e0e8aba8

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: Bypass UAC via CMSTP
id: e66779cc-383e-4224-a3a4-267eeb585c40
status: test
description: Detect commandline usage of Microsoft Connection Manager Profile Installer (cmstp.exe) to install specially formatted local .INF files
references:
    - https://eqllib.readthedocs.io/en/latest/analytics/e584f1a1-c303-4885-8a66-21360c90995b.html
    - https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1218.003/T1218.003.md
    - https://lolbas-project.github.io/lolbas/Binaries/Cmstp/
author: E.M. Anhaus (originally from Atomic Blue Detections, Endgame), oscd.community
date: 2019-10-24
modified: 2022-08-30
tags:
    - attack.privilege-escalation
    - attack.stealth
    - attack.t1548.002
    - attack.t1218.003
logsource:
    category: process_creation
    product: windows
detection:
    selection_img:
        - Image|endswith: '\cmstp.exe'
        - OriginalFileName: 'CMSTP.EXE'
    selection_cli:
        CommandLine|contains:
            - '/s'
            - '-s'
            - '/au'
            - '-au'
            - '/ni'
            - '-ni'
    condition: all of selection*
falsepositives:
    - Legitimate use of cmstp.exe utility by legitimate user
level: high

Original YAML and metadata in JSON

False positives

• Legitimate use of cmstp.exe utility by legitimate user

Source references

• https://eqllib.readthedocs.io/en/latest/analytics/e584f1a1-c303-4885-8a66-21360c90995b.html
• https://github.com/redcanaryco/atomic-red-team/blob/f339e7da7d05f6057fdfcdd3742bfcf365fee2a9/atomics/T1218.003/T1218.003.md
• https://lolbas-project.github.io/lolbas/Binaries/Cmstp/