Every few months our computers at work come down with some sort of computer virus. Most of these are launched unwittingly by the usual suspects - people running joke programs that they get in the mail, or people reading Word documents that came from an infected source.
I try to be careful about mail attachments. Joke programs, or any programs at all that I haven't specifically requested, go straight into the garbage. I also am careful about opening Word documents, and I always disable macros when I do open them. I have yet to see any content spoiled by disabling Word macros, but no doubt I eventually will. Too bad.
However, some of the viruses that we have encountered are fairly nasty, and they propagate through the local network as soon as any computer in the office is infected. One variant, called the QAZ trojan, replaced the normal code for Notepad with a version that spawned itself to all of the computers it could find on the LAN, and then ran the old version of Notepad (renamed to Note.com) so that no one was the wiser. Eventually one of the anti-virus programs noticed it, but it made the rounds a few times before we finally eradicated it.
We took some heart in the fact that Microsoft itself got infected by the same virus, which let hackers get read access to some of the OS code. So even the giant corporations are vulnerable to these attacks.
The computer analog of hygiene is becoming a necessity. One must "wash one's hands" frequently by running anti-virus programs, and when it comes to running foreign programs, "don't put that in your mouth - you don't know where it's been!" For the ultimate in safety, just turn the computer off and use paper and a pencil. Just keep the pencil out of your mouth.
You can respond to my ranting here.
When in Rome, rant as the Romans do.