What is a zombie computer?

Imagine that the Internet is a city. It would undoubtedly be the most remarkable & diverse city on the planet, but it would also be incredibly seedy & dangerous. You could find the world's most comprehensive libraries there alongside X-rated theaters. Inside this city, you would also discover that not everyone is who they seem to be - even yourself. You might find out that you've been misbehaving, although you don't remember it. Like the unwitting agent in. "The Manchurian Candidate", you discover you've been doing someone else's bidding & you have no idea how to stop it. A zombie computer is very much like the agent in "The Manchurian Candidate". A hacker secretly infiltrates an unsuspecting victim's computer & uses it to conduct illegal activities. The user generally remains unaware that his computer has been taken over - he can still use it, thought it might slow considerably. As his computer begins to either send out massive amounts of spam or attack Web pages, he becomes the focal point for any investigations involving his computer's suspicious activities.