Zombie Computer Armies

Botnets. You may not have heard of them, but their invisible nature makes them all the more dangerous. And you may already be both a victim and an accomplice in a botnet operation. Because everything in the high-tech world needs an acronym or abbreviation, a botnet is actually short for a robot network. Think of it as a massive super-computer army with your computer potentially one of the many conscripted ranks.

Here's how a botnet starts: a malicious hacker or hackers sends a virus or discovers your machine online, plants a program to gain control of the resources and information, and then uses your machine to search for more vulnerable computers to take over. Botnets can quickly grow in size to tens or hundreds of thousands of computers, all waiting to be commanded by their botnet master or "botherder." Botnet computers can then be used for plenty of nefarious means ranging from sending spam, denial-of-service attacks, identity theft, and much more.

So, hypothetically, a hacker infiltrates your computer and steals your banking information, and then lies dormant by hiding in the background. You never know how you lost all this money, and you can't find any problem on your computer. Then when the botmaster feels like overwhelming or crashing a mid-size e-commerce Web site, he forces your computer to act in concert with hundreds of thousands of others, all sending huge streams of data at a network. The e-commerce site is rendering useless. That's when the botmaster faxes the e-commerce site a note and demands $20,000 to stop the attack. The e-commerce site complies because it's embarrassed and doesn't want its clients to know it was victimized. And through it all, both you as the initial victim and the e-commerce site don't report it to the authorities. In your case you didn't realize what happened, and with the e-commerce site it's about protecting its reputation.

But as I say, there are far-reaching implications for botnets beyond that example. Even terrorism or organized crime. The FBI's cyber division is involved, and it says there are more than 100 active investigations into botnets around the world. The experts I've talked to over the years call botnets one of, if not THE largest threat to Internet security. Today the FBI announced that one million more machines have been co-opted into botnets since they began "Operation Bot Roast" back in June, causing more than $20 million in damage.

Tonight on the CBS Evening News with Katie Couric we'll look at this growing online scourge and tell you a few basic tips on how to protect yourself.