Suspicious Files With System DLL Name In Unsuspected Locations (via file_event)

title: Suspicious Files With System DLL Name In Unsuspected Locations (via file_event)
id: 93e95587-e40d-5544-9eed-5cb55b43059c
status: stable
description: This rule detects the creation of a file with the ".dll" extension that has the name of a System DLL in uncommon or unsuspected locations. (Outisde of "System32", "SysWOW64", etc.). It is highly recommended to perform an initial baseline before using this rule in production.
references:
    - https://attack.mitre.org/techniques/T1036/005/
    - Internal Research
author: Huntrule Team
date: 2026-02-21
tags:
    - attack.stealth
    - attack.t1036.005
logsource:
    category: file_event
    product: windows
detection:
    selection:
        TargetFilename|endswith:
            - '\secur32.dll'
            - '\tdh.dll'
    filter_main_generic:
        TargetFilename|contains:
            - 'C:\$WINDOWS.~BT\'
            - 'C:\$WinREAgent\'
            - 'C:\Windows\SoftwareDistribution\'
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
            - 'C:\Windows\WinSxS\'
            - 'C:\Windows\uus\'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: medium
regression_tests_path: regression_data/rules/windows/file/file_event/file_event_win_creation_system_dll_files/info.yml