I found the solution:

Winexit.scr: Windows Exit Screen Saver

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WinExit is a screen saver that logs the current user off after the specified time has elapsed. In other respects it is similar to other screen savers and can be configured and tested on the Screen Saver tab of the Display Properties dialog box in Control Panel.

WinExit displays a dialog box containing the countdown timer and a user-defined message. When the countdown timer reaches zero, the logoff process is initiated