Windows notices inactivity of a logon session, and if the amount of inactive time exceeds the inactivity limit, then the screen saver will run, locking the session. Vulnerability: If a user forgets to lock their computer when they walk away it is possible that a passerby will hijack it. Counter Measure: Configure this policy setting to 900 seconds (15 minutes) so that the risk of a user's desktop session being hijacked by a passerby is reduced. Potential Impact: The screen saver will automatically activate when the computer has been unattended for the amount of time specified. The impact should be minimal since the screen saver is enabled by default. Fix: (1) GPO: Computer Configuration\Windows Settings\Security Settings\Local Policies\Security Options\Interactive logon: Machine inactivity limit (2) REG: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Policies\System!InactivityTimeoutSecs