T1546.002: Screensaver

MITRE ATT&CK® Enterprise technique

Description

Adversaries may establish persistence by executing malicious content triggered by user inactivity. Screensavers are programs that execute after a configurable time of user inactivity and consist of Portable Executable (PE) files with a .scr file extension.(Citation: Wikipedia Screensaver) The Windows screensaver application scrnsave.scr is located in <code>C:\Windows\System32</code>, and <code>C:\Windows\sysWOW64</code> on 64-bit Windows systems, along with screensavers included with base Windows installations.

The following screensaver settings are stored in the Registry (<code>HKCU\Control Panel\Desktop</code>) and could be manipulated to achieve persistence:

• <code>SCRNSAVE.exe</code> - set to malicious PE path
• <code>ScreenSaveActive</code> - set to '1' to enable the screensaver
• <code>ScreenSaverIsSecure</code> - set to '0' to not require a password to unlock
• <code>ScreenSaveTimeout</code> - sets user inactivity timeout before screensaver is executed

Adversaries can use screensaver settings to maintain persistence by setting the screensaver to run malware after a certain timeframe of user inactivity.(Citation: ESET Gazer Aug 2017)

Detection

(no detection guidance published)

Data sources

• (none listed)

References

• ATT&CK page: https://attack.mitre.org/techniques/T1546/002
• ATT&CK Enterprise matrix: https://attack.mitre.org/matrices/enterprise/