The BBC has done informal test of computers on the Internet to see how often they were attacked. Seems their results are about once an hour. My experience has shown that a new computer will be attacked within about 3 or 4 minutes of it's connection to the Internet.

In any event, PROTECT YOUR PC! I don't care what or why you are using the PC. I don't care how unimportant and insignificant you and your Internet use are. Even if you don't care about the computer or your data, you don't want the PC used for illegal purposes by organized crime in Russia, or elsewhere. You could end up with the FBI at your doorstep because your computer was unknowingly used by an indentity theft ring based overseas.