According to NPR - Microsoft just released its ninth Security Intelligence Report. The focus is on botnets. Microsoft cleaned 6.5 million computers from botnet infections in the three months April – June 2010. That's double the number a year ago. And remember, that's just those that have been cleaned. There are likely many millions more that haven't been.
If you've been infected you don't control what your computer does, the botnet does. You probably won't even notice as your computer becomes a typhoid Mary, spewing viruses, spam and phishing attempts, or used to launch denial of service attacks. Without you even knowing it you are the problem.
The United States has more zombie computers than any other country in the world, and this is completely avoidable.
I downloaded a small free detection program from Microsoft today to test my computer and I recommend you take 5 minutes and do the same to secure your computer as a poker player, especially.