My wife went on WebMD yesterday, looking for information about a condition a relative might have. She went through the usual drill — typing the name of the condition into WebMD's "Search" field, and then reviewing the results to see where to click next.
WebMD links to outside sources of information as well as information they create, and they rank search results by some percentage/relevance algorythm. My wife picked one of the top two or three results. She got sent, instead, into one of those porn sites that opens two new windows every time you try to close one, each one more repulsive than the one before. She finally stopped the madness, but then a cartoon bubble popped up from the toolbar saying the computer had been infected with a virus.
I got on the computer this morning to see what was up. According to McAfee, a "medium-level worm" type of virus had infected our computer. McAfee could identify it, but could neither remove nor quarantine it.
After searching around, I found a scanner for this specific type of virus, and apparently that did the trick, although, as I write, McAfee is scanning my computer again, and has found some other area of infection that we didn't have before. So I'm not quite done yet.
Apart from having anti-virus software, to keep your computer free of viruses, the best practices are generally said to be — don't open attachments to e-mail from sources you don't know; don't open executable files. Right? My wife did neither of these things. She just clicked on an innocuous link. A link tagged with the name of a medical condition.
It could happen to her, it could happen to you. I don't know what advice to give you. Don't click in unfamiliar territory? But that's the whole point of the Internet. Distressing.