Windows: Detect UAC bypass attempts via winsat.exe path parsing from user temp

Flags file activity targeting Temp\system32\winsat.exe (or winmm.dll) under C:\Users\ consistent with a UAC bypass attempt.

FreeReviewedSigma · High · v2

Product: windows
Category: file_event
Author: Christian Burkard (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2021-08-30
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Priv Esc → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
- T1548.002Bypass User Account Control
Defense Evasion
- T1548.002Bypass User Account Control
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule identifies file events where the target filename starts under C:\Users\ and ends with the specific temp-based paths used to invoke winsat.exe (and related system32 DLL usage). Such behavior is commonly associated with UAC bypass techniques that rely on path parsing quirks to reach protected binaries. The detection relies on filesystem telemetry that records the TargetFilename field in Windows file events.

Reporting behind it

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Windows: Detect UAC bypass attempts via winsat.exe path parsing from user temp

Pivot detection · T1548.002 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

file-event-detect-uac-bypass-attempt-via-winsat-exe-path-parsing-in-temp-155dbf56

title: "Windows: Detect UAC bypass attempts via winsat.exe path parsing from user temp"
id: 4d1db176-cfc7-481a-82ae-e3f43a42bce6
status: test
description: This rule identifies file events where the target filename starts under C:\Users\ and ends with the specific temp-based paths used to invoke winsat.exe (and related system32 DLL usage). Such behavior is commonly associated with UAC bypass techniques that rely on path parsing quirks to reach protected binaries. The detection relies on filesystem telemetry that records the TargetFilename field in Windows file events.
references:
  - https://github.com/hfiref0x/UACME
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_uac_bypass_winsat.yml
author: Christian Burkard (Nextron Systems), Huntrule Team
date: 2021-08-30
modified: 2022-10-09
tags:
  - attack.privilege-escalation
  - attack.t1548.002
logsource:
  category: file_event
  product: windows
detection:
  selection:
    TargetFilename|startswith: C:\Users\
    TargetFilename|endswith:
      - \AppData\Local\Temp\system32\winsat.exe
      - \AppData\Local\Temp\system32\winmm.dll
  condition: selection
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 155dbf56-e0a4-4dd0-8905-8a98705045e8
    type: derived

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