A screen saver can protect the system as well as the data from unauthorized access if the computer is left unattended without the user logging off. An automatic function should be provided to activate the screen saver after a specified number of minutes, and it should also be possible to activate it using shortcut keys. A security system should provide screen savers for DOS and Windows. Two different technologies are used for screen savers in Windows. The first uses the internal Windows screen saver function, which is activated from the Control Panel. The second uses a special program that runs in the background in Windows. Both technologies have their advantages and disadvantages. DOS sessions have always presented particular problems for screen savers in Windows. If a DOS window has the focus, a Windows screen saver will not start. Many products apply the solution of using a VxD or DOS TSR with the screen saver in these circumstances. In Windows, the screen saver is controlled from the Control Panel, which inserts the following line in system.ini :
SCRNSAVE.EXE=BWINSAVE.SCR
Many people use the screen saver supplied with Windows. This is satisfactory if the computer is used by only one person. If a number of people use the computer, the standard Windows screen saver creates password problems. All users need to know the screen saver passwords of all the computers they use. This impairs security, and make administration difficult. A screen saver should therefore prompt for the password entered by the user when he or she logged on. That way, the user always types the same screen saver password regardless of the computer he or she is logged onto.
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