---
Name: Regasm.exe
Description: Part of .NET
Author: 'Oddvar Moe'
Created: 2018-05-25
Commands:
  - Command: regasm.exe AllTheThingsx64.dll
    Description: Loads the target .DLL file and executes the RegisterClass function.
    Usecase: Execute code and bypass Application whitelisting
    Category: AWL Bypass
    Privileges: Local Admin
    MitreID: T1218.009
    OperatingSystem: Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11
    Tags:
      - Execute: DLL
      - Input: Custom Format
  - Command: regasm.exe /U AllTheThingsx64.dll
    Description: Loads the target .DLL file and executes the UnRegisterClass function.
    Usecase: Execute code and bypass Application whitelisting
    Category: Execute
    Privileges: User
    MitreID: T1218.009
    OperatingSystem: Windows vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11
    Tags:
      - Execute: DLL
      - Input: Custom Format
Full_Path:
  - Path: C:\Windows\Microsoft.NET\Framework\v2.0.50727\regasm.exe
  - Path: C:\Windows\Microsoft.NET\Framework64\v2.0.50727\regasm.exe
  - Path: C:\Windows\Microsoft.NET\Framework\v4.0.30319\regasm.exe
  - Path: C:\Windows\Microsoft.NET\Framework64\v4.0.30319\regasm.exe
Detection:
  - Sigma: https://github.com/SigmaHQ/sigma/blob/6312dd1d44d309608552105c334948f793e89f48/rules/windows/process_creation/proc_creation_win_lolbin_regasm.yml
  - Elastic: https://github.com/elastic/detection-rules/blob/12577f7380f324fcee06dab3218582f4a11833e7/rules/windows/execution_register_server_program_connecting_to_the_internet.toml
  - Splunk: https://github.com/splunk/security_content/blob/bc93e670f5dcb24e96fbe3664d6bcad92df5acad/docs/_stories/suspicious_regsvcs_regasm_activity.md
  - Splunk: https://github.com/splunk/security_content/blob/bee2a4cefa533f286c546cbe6798a0b5dec3e5ef/detections/endpoint/detect_regasm_with_network_connection.yml
  - IOC: regasm.exe executing dll file
Resources:
  - Link: https://pentestlab.blog/2017/05/19/applocker-bypass-regasm-and-regsvcs/
  - Link: https://oddvar.moe/2017/12/13/applocker-case-study-how-insecure-is-it-really-part-1/
  - Link: https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1218.009/T1218.009.md
Acknowledgement:
  - Person: Casey Smith
    Handle: '@subtee'