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 C:\Windows\System32\, and C:\Windows\sysWOW64\ on 64-bit Windows systems, along with screensavers included with base Windows installations. The following screensaver settings are stored in the Registry (HKCU\Control Panel\Desktop\) and could be manipulated to achieve persistence: * SCRNSAVE.exe - set to malicious PE path * ScreenSaveActive - set to '1' to enable the screensaver * ScreenSaverIsSecure - set to '0' to not require a password to unlock * ScreenSaveTimeout - 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)

Linked Issues

Issuelinks
Linktype Issue
is related to Techniques
is blocked by Execution Prevention
is blocked by Detect Screensaver-Based Persistence via Registry and Execution Chains
is blocked by Disable or Remove Feature or Program
is blocked by Asset Inventories
is blocked by Secure Baseline Configurations
is blocked by Least Functionality
is blocked by Continuous Monitoring
is blocked by Malicious Code Protection (Anti-Malware)
is blocked by Endpoint File Integrity Monitoring (FIM)
is blocked by Input Data Validation
is blocked by Vulnerability Scanning
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