Regsvr32 DLL Execution With Unusual Extension (via process_creation)

title: Regsvr32 DLL Execution With Unusual Extension (via process_creation)
id: f8f92036-c179-5f80-83fe-e355ff0e3bd4
status: stable
description: This rule detects a "regsvr32" execution where the DLL doesn't contain a common file extension.
references:
    - https://attack.mitre.org/techniques/T1574/
    - https://app.any.run/tasks/34221348-072d-4b70-93f3-aa71f6ebecad/
author: Huntrule Team
date: 2026-03-19
tags:
    - attack.privilege-escalation
    - attack.persistence
    - attack.stealth
    - attack.t1574
    - attack.execution
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        - Image|endswith: '\regsvr32.exe'
        - OriginalFileName: 'REGSVR32.EXE'
    filter_main_legit_ext:
        CommandLine|contains:
            - '.ax'
            - '.cpl'
            - '.dll'
            - '.ocx'
    filter_optional_pascal:
        CommandLine|contains: '.ppl'
    filter_optional_avg:
        CommandLine|contains: '.bav'
    filter_main_null_4688:
        CommandLine:
    filter_main_empty_4688:
        CommandLine: ''
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - Unknown
level: medium