COM Hijacking

UAC Bypass/Defense Evasion, Persistence

The Microsoft Component Object Model (COM) is a platform-independent, distributed, object-oriented system for creating binary software components that can interact. COM is the foundation technology for Microsoft's OLE (compound documents), ActiveX (Internet-enabled components), as well as others.

In this lab we will execute a file-less UAC bypass technique.

Execution

On the compromised system, change the HKEY_LOCAL_MACHINE\SOFTWARE\Classes\mscfile\shell\open\command default value to point to your binary. In this case I chose powershell.exe:

By default, launching Windows Event Viewer calls under the hood:"C:\Windows\system32\mmc.exe" "C:\Windows\system32\eventvwr.msc" /s

Since we hijacked the HKEY_LOCAL_MACHINE\SOFTWARE\Classes\mscfile\shell\open\command to point to powershell, when launching Even Viewer, the powershell is invoked instead:

Observation

Monitoring registry for changes in HKEY_CLASSES_ROOT\mscfile\shell\open\command can reveal this hijaking activity:

References

Event Triggered Execution: Component Object Model Hijacking, Sub-technique T1546.015 - Enterprise | MITRE ATT&CK®

“Fileless” UAC Bypass Using eventvwr.exe and Registry Hijackingenigma0x3

Bypassing Windows User Account Control (UAC) and ways of mitigationGreyHatHacker.NET

FuzzySecurity | Anatomy of UAC Attacks