Windows: WerFault.exe/wer.dll File Creation in Uncommon Locations

Alerts on newly created WerFault.exe or wer.dll in non-standard locations, suggesting potential DLL hijacking activity.

FreeReviewedSigma · Medium · v2

Product: windows
Category: file_event
Author: frack113 (SigmaHQ), DRL 1.1
Published: 2022-05-09
Updated: 2026-07-31

ATT&CK techniques

Execution → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
- T1574.001DLL
Persistence
- T1574.001DLL
Priv Esc
- T1574.001DLL
Defense Evasion
- T1574.001DLL
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags the creation of files named WerFault.exe or wer.dll when they appear in locations other than common Windows system directories. Attackers may use these binaries for DLL hijacking or related persistence to execute malicious code under trusted Windows paths. It relies on Windows file creation telemetry that includes the full target path and the creating process image, and it excludes events where the creating process ends with wuaucltcore.exe.

Reporting behind it

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Windows: WerFault.exe/wer.dll File Creation in Uncommon Locations

Pivot detection · T1574.001 · 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.

windows-werfault-exe-wer-dll-created-in-uncommon-directory-28a452f3

title: "Windows: WerFault.exe/wer.dll File Creation in Uncommon Locations"
id: 7e45ff87-cf72-4fd3-93d6-8d80eef36805
status: test
description: This rule flags the creation of files named WerFault.exe or wer.dll when they appear in locations other than common Windows system directories. Attackers may use these binaries for DLL hijacking or related persistence to execute malicious code under trusted Windows paths. It relies on Windows file creation telemetry that includes the full target path and the creating process image, and it excludes events where the creating process ends with wuaucltcore.exe.
references:
  - https://www.bleepingcomputer.com/news/security/hackers-are-now-hiding-malware-in-windows-event-logs/
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_werfault_dll_hijacking.yml
author: frack113, Huntrule Team
date: 2022-05-09
modified: 2026-05-18
tags:
  - attack.privilege-escalation
  - attack.persistence
  - attack.execution
  - attack.stealth
  - attack.t1574.001
logsource:
  product: windows
  category: file_event
detection:
  selection:
    TargetFilename|endswith:
      - \WerFault.exe
      - \wer.dll
  filter_main_known_locations:
    TargetFilename|startswith:
      - C:\Windows\SoftwareDistribution\
      - C:\Windows\System32\
      - C:\Windows\SysWOW64\
      - C:\Windows\WinSxS\
      - C:\Windows\UUS\
  filter_main_process:
    Image|endswith: \wuaucltcore.exe
  condition: selection and not 1 of filter_main_*
falsepositives:
  - Unknown
level: medium
license: DRL-1.1
related:
  - id: 28a452f3-786c-4fd8-b8f2-bddbe9d616d1
    type: derived

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