Syssetup.dll

Commands

1. AWL BypassUser T1218.011

   Run local or remote script(let) code through INF file specification (Note May pop an error window).

   rundll32 syssetup.dll,SetupInfObjectInstallAction DefaultInstall 128 {PATH_ABSOLUTE:.inf}

   Execute the specified (local or remote) .wsh/.sct script with scrobj.dll in the .inf file by calling an information file directive (section name specified).

   os: Windows 10, Windows 11

   Execute: INF

2. ExecuteUser T1218.011

   Load an executable payload.

   rundll32 syssetup.dll,SetupInfObjectInstallAction DefaultInstall 128 {PATH_ABSOLUTE:.inf}

   Launch an executable file via the SetupInfObjectInstallAction function and .inf file section directive.

   os: Windows 10, Windows 11

   Execute: INF

Detection

• Sigma https://github.com/SigmaHQ/sigma/blob/62d4fd26b05f4d81973e7c8e80d7c1a0c6a29d0e/rules/windows/process_creation/proc_creation_win_rundll32_susp_activity.yml
• Splunk https://github.com/splunk/security_content/blob/86a5b644a44240f01274c8b74d19a435c7dae66e/detections/endpoint/detect_rundll32_application_control_bypass___syssetup.yml

Code samples

• https://raw.githubusercontent.com/huntresslabs/evading-autoruns/master/shady.inf
• https://gist.github.com/enigma0x3/469d82d1b7ecaf84f4fb9e6c392d25ba#file-backdoor-minimalist-sct
• https://gist.github.com/homjxi0e/87b29da0d4f504cb675bb1140a931415

Resources

• https://twitter.com/pabraeken/status/994392481927258113
• https://twitter.com/harr0ey/status/975350238184697857
• https://twitter.com/bohops/status/975549525938135040
• https://windows10dll.nirsoft.net/syssetup_dll.html