sigmalowHunting

RegAsm.EXE Execution Without CommandLine Flags or Files

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.

MITRE ATT&CK

T1218.009

defense-evasion

Detection Query

selection_img:
  - Image|endswith: \RegAsm.exe
  - OriginalFileName: RegAsm.exe
selection_cli:
  CommandLine|endswith:
    - RegAsm
    - RegAsm.exe
    - RegAsm.exe"
    - RegAsm.exe'
condition: all of selection_*

Author

frack113

Created

2025-06-04

Data Sources

windowsProcess Creation Events

Platforms

windows

References

Tags

attack.defense-evasionattack.t1218.009

Raw Content

title: RegAsm.EXE Execution Without CommandLine Flags or Files
id: 651f87f7-12db-47f9-84c5-f27b081b94b6
status: experimental
description: |
    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://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: frack113
date: 2025-06-04
tags:
    - attack.defense-evasion
    - 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:
    - Legitimate use of Regasm by developers.
# Note: You can increase after an initial baseline
level: low