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

SIGMA detection rule by frack113 · NOASSERTION

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.

title: Creation of WerFault.exe/Wer.dll in Unusual Folder
id: 28a452f3-786c-4fd8-b8f2-bddbe9d616d1
status: test
description: 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.
references:
    - https://www.bleepingcomputer.com/news/security/hackers-are-now-hiding-malware-in-windows-event-logs/
author: frack113
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\' # covers both C:\Windows\UUS\arm64\ and C:\Windows\UUS\packages\
    filter_main_process:
        Image|endswith: '\wuaucltcore.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium

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0f15e4f1-673a-4cf6-bda2-f25e317e6b6f

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Executable code, not a declarative rule

This submission is arbitrary [[ currentRule.format ? currentRule.format.toUpperCase() : '' ]] code, not a declarative detection rule — review it as you would any script before running it, and note that it cannot be safely aggregated or auto-executed alongside YARA/Sigma/Suricata/CRS rules.

Rejected pattern present

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