Creation of WerFault.exe/Wer.dll in Unusual Folder (via file_event)

title: Creation of WerFault.exe/Wer.dll in Unusual Folder (via file_event)
id: adad2729-ac87-5d01-acfb-f014ce6d1f1b
status: stable
description: This rule 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://attack.mitre.org/techniques/T1574/001/
    - https://www.bleepingcomputer.com/news/security/hackers-are-now-hiding-malware-in-windows-event-logs/
author: Huntrule Team
date: 2026-02-10
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