Windows UAC Bypass via NTFS Reparse Point: wusa.exe DLL Hijacking Process Behavior

title: "Windows UAC Bypass via NTFS Reparse Point: wusa.exe DLL Hijacking Process Behavior"
id: 2e6429c7-9f18-49db-93c5-de9d4f70bc2b
status: test
description: This rule flags a process-creation sequence consistent with a UAC bypass technique that uses an NTFS reparse point and wusa.exe DLL hijacking. It matches wusa.exe executions with specific command-line patterns and high/system integrity context, as well as a parent dism.exe invocation indicative of package/handler staging. Telemetry required is Windows process creation with full command lines and process integrity level data.
references:
  - https://github.com/hfiref0x/UACME
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_uac_bypass_ntfs_reparse_point.yml
author: Christian Burkard (Nextron Systems), Huntrule Team
date: 2021-08-30
modified: 2024-12-01
tags:
  - attack.privilege-escalation
  - attack.t1548.002
logsource:
  category: process_creation
  product: windows
detection:
  selection1:
    CommandLine|startswith: '"C:\Windows\system32\wusa.exe"  /quiet C:\Users\'
    CommandLine|endswith: \AppData\Local\Temp\update.msu
    IntegrityLevel:
      - High
      - System
      - S-1-16-16384
      - S-1-16-12288
  selection2:
    ParentCommandLine: '"C:\Windows\system32\dism.exe" /online /quiet /norestart /add-package /packagepath:"C:\Windows\system32\pe386" /ignorecheck'
    IntegrityLevel:
      - High
      - System
    CommandLine|contains|all:
      - C:\Users\
      - \AppData\Local\Temp\
      - \dismhost.exe {
    Image|endswith: \DismHost.exe
  condition: 1 of selection*
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 39ed3c80-e6a1-431b-9df3-911ac53d08a7
    type: derived