I have no idea why, but in all the years I've been online, even when I had, for several years, no anti-virus protection at all, I've been extremely lucky and only once had a trojan invade my computer. Other than that one instance, no anti-virus program has ever recorded anything at all.

Of course, my online habits are pretty clean, and I'm not addicted to exchanging cute or jokey emails with all my correspondents - one of my relatives is still a little miffed that I refused to accept her constant stream of glurge, prayer chain letters, multi-forwarded jokes and other junk.