Possible RegAsm.EXE Execution Without CommandLine Flags or Files (via process_creation)

title: Possible RegAsm.EXE Execution Without CommandLine Flags or Files (via process_creation)
id: ae436197-49e6-521d-8cb1-62aa1b4b2024
status: stable
description: This rule detects the execution of "RegAsm.exe" without a commandline flag or file, which might indicate potential process injection activity. Usually "RegAsm.exe" should point to a dedicated DLL file or call the help with the "/?" flag.
references:
    - https://attack.mitre.org/techniques/T1218/009/
    - https://www.mcafee.com/blogs/other-blogs/mcafee-labs/agent-teslas-unique-approach-vbs-and-steganography-for-delivery-and-intrusion/
    - https://www.zscaler.fr/blogs/security-research/threat-actors-exploit-cve-2017-11882-deliver-agent-tesla
    - https://learn.microsoft.com/en-us/dotnet/framework/tools/regasm-exe-assembly-registration-tool
    - https://app.any.run/tasks/ea944b89-69d8-49c8-ac1f-5c76ad300db2
    - https://www.joesandbox.com/analysis/1467354/0/html
author: Huntrule Team
date: 2026-05-25
tags:
    - attack.stealth
    - attack.t1218.009
logsource:
    product: windows
    category: process_creation
detection:
    selection_img:
        - Image|endswith: '\RegAsm.exe'
        - OriginalFileName: 'RegAsm.exe'
    selection_cli:
        CommandLine|endswith:
            - 'RegAsm'
            - 'RegAsm.exe'
            - 'RegAsm.exe"'
            - "RegAsm.exe'"
    condition: all of selection_*
falsepositives:
    - Unknown
level: low