One of my hats at my employer deals with computer security. Not necessarily physical security (although as a system administrator I think about that too) but with protecting the computing infrastructure that I'm responsible from crackers, viruses, and clueless users. With a bit of planning and thought it's a lot easier than it seems. However if one acts without thinking then bad things happen.
At work computers are not allowed on the network without the proper security patches applied and, if the OS supports one, a real time antivirus scanner. if one is caught on the network it gets blocked pretty quick. If the same user keeps doing it then management gets involved. While I'm a 'senior person' I'd just as well stay out of managements line of fire when bad things are happening. Unless I get to figure out what happened. Thats fun stuff! And fodder for another story.
Now Thing1 is off at college, having had the computer staff there check his computers for up to date patches and AV software before the were allowed on the net. Given the problems some colleges have with viruses I can see their point. So I got a good laugh today when Thing1 called me at lunch (family time cell packages are real handy!) and said he had stopped down at the computer lab to inquire about a job and the staff
was battling a virus outbreak. Seems one of the staff put a students PC on the public network to patch it and it had a worm of some kind and it started hitting the network. Hard.
This broke a couple of basic computer security rules. Never, ever, put a unknown computer on a public network until you are sure there are no viruses or worms on it. Then you patch it (off line). Once you are sure that it has no viruses or worms and that the mandatory set of patches are installed do you put it on the net. And then you check it again. I prefer the Microsoft Baseline Security Analyser for Windows systems but there are other ways.
Save the Internet - keep your systems patched!