My son is a geek in network security. He takes classes called things like "Ethical Hacking"! He told me if you go on the internet without any protection, the time it will take you to get a virus is 3 seconds. Eeeeyowch!
He tells me all these horror stories when he comes home from conventions about the newest evil stuff people can do to your computer. Sometimes I wish he'd been a plumber, but then when I have something go wrong with my computer I'm terribly glad I can just pick up the phone and have him fix it!