Creation of WerFault.exe/Wer.dll in Unusual Folder

Dec 9, 2025 · attack.privilege-escalation attack.persistence attack.defense-evasion attack.t1574.001 ·

Detects the creation of a file named "WerFault.exe" or "wer.dll" in an uncommon folder, which could be a sign of WerFault DLL hijacking.

Sigma rule (View on GitHub)

 1title: Creation of WerFault.exe/Wer.dll in Unusual Folder
 2id: 28a452f3-786c-4fd8-b8f2-bddbe9d616d1
 3status: test
 4description: Detects the creation of a file named "WerFault.exe" or "wer.dll" in an uncommon folder, which could be a sign of WerFault DLL hijacking.
 5references:
 6    - https://www.bleepingcomputer.com/news/security/hackers-are-now-hiding-malware-in-windows-event-logs/
 7author: frack113
 8date: 2022-05-09
 9modified: 2025-12-03
10tags:
11    - attack.privilege-escalation
12    - attack.persistence
13    - attack.defense-evasion
14    - attack.t1574.001
15logsource:
16    product: windows
17    category: file_event
18detection:
19    selection:
20        TargetFilename|endswith:
21            - '\WerFault.exe'
22            - '\wer.dll'
23    filter_main_known_locations:
24        TargetFilename|startswith:
25            - 'C:\Windows\SoftwareDistribution\'
26            - 'C:\Windows\System32\'
27            - 'C:\Windows\SysWOW64\'
28            - 'C:\Windows\WinSxS\'
29            - 'C:\Windows\UUS\arm64\'
30    condition: selection and not 1 of filter_main_*
31falsepositives:
32    - Unknown
33level: medium

References

Hackers are now hiding malware in Windows Event Logs

Security researchers have noticed a malicious campaign that used Windows event logs to store malware, a technique that has not been previously documented publicly for attacks in the wild.

Read More

Creation of WerFault.exe/Wer.dll in Unusual Folder

Sigma rule (View on GitHub)

References

Hackers are now hiding malware in Windows Event Logs

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