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Screensavers and Security


Screensavers are good for three things: protecting your monitor from phosphor-burn, which is not very likely today, keeping you amused, which is most important :), and hiding the content of your screen from curious eyes, which may be important. Well, if you're playing Quake and the boss happens to drop in anyway. No, not my boss - he'd surely look for the next unused machine ;)


A screensaver that can be shut down by everybody is not of much use for security. The feeble security that can be implemented by starting a screensaver with password protection is not worth a penny anyway. A machine somebody has physical access to is as good as open. An intruder on your personal data would simply reboot the machine with the BRS and be done with it.


Now, at least they serve to protect your personal data on a NT-box. Note that there is absolutely no protection (against a person physically accessing your machine) implemented by Microsoft on any 3x- or 9x-machine for you personal data!


Well, if you keep this in mind, you can do the little that can be done with a screensaver.


In the last time the web gets floated with screensavers from an application called something like "screensaver factory". I don't know the exact name, but that doesn't matter. The application allows you to put your own images or animations into a screensaver that is an example of sloppy programming. To say the least. Eye-candy, nothing else.


A screensaver that's worth to be downloaded gives as much security as a screensaver can. That means: Disabling the Ctrl-Alt-Del, Alt-F4, Alt-F10, Alt-Tab and some other key-combinations that have a special meaning in Windows. The Wink(e)y has to be handled seperately, as far as I know. Check it out.

How can this be done? It's quite simple. Windows talks to a screensaver via commandline.


/c : show the options - provide a special form for that.

/p : make a preview

/s : run the screensaver


Those are not all options. To see them all, look in the MSDN.

When making the Matrix-screensaver, I used the code beyond. All functions and constants can be found within the API-viewer, so I refrained from showing the declares here. I pasted the function I used to hide the taskbar in full, it's worth more this way :)


Showcursor hides or shows the mousepointer:

' hide the cursor. set to value <> 0 to un-hide it.
Call ShowCursor(0)

To start the screensaver:
'called to start the screensaver.

'call with FALSE instead of TRUE to stop it.
Call SystemParametersInfo(SPI_SETSCREENSAVEACTIVE, True, 0, 0)

To stop the taskbar from being shown (and your screensaver accessed by it), use this function:
'this function hides the taskbar(true) or

'un-hides it (false).
CoverScreen True

Public Sub CoverScreen(Maximize As Boolean)
Dim TaskBarHandle As Long
    If Maximize Then
        TaskBarHandle = FindWindow("Shell_traywnd", "")
       Call SetWindowPos(TaskBarHandle, 0, 0, 0, 0, 0, _

SWP_HIDEWINDOW)
    Else

        TaskBarHandle = FindWindow("Shell_traywnd", "")
        Call SetWindowPos(TaskBarHandle, 0, 0, 0, 0, 0, _

SWP_SHOWWINDOW)
    End If
End Sub


Don't forget to un-hide the taskbar to shut down your screensaver. If all fails and you don't see it after your screensaver has run (happens to me while debugging ;) ), either try running the screensaver again without bugs, or restart windows.