Windows: Command-line execution of cmstp.exe with INF install/silent/autobind flags (UAC bypass pattern)

title: "Windows: Command-line execution of cmstp.exe with INF install/silent/autobind flags (UAC bypass pattern)"
id: 3c7e77a0-1616-4405-9594-e070d08f0d00
status: test
description: This rule flags Windows process creation where cmstp.exe is executed with command-line switches commonly used to install specially formatted INF files and suppress interactive behavior. Attackers abuse cmstp.exe to gain elevated capabilities while reducing user visibility, making this activity high risk. The detection relies on process creation telemetry including the image path/name and the presence of specific command-line flags associated with the installer workflow.
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/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_uac_bypass_cmstp.yml
author: E.M. Anhaus (originally from Atomic Blue Detections, Endgame), oscd.community, Huntrule Team
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
license: DRL-1.1
related:
  - id: e66779cc-383e-4224-a3a4-267eeb585c40
    type: derived