Internet security experts today warned that vast networks of home computers are being hijacked, many without the owner's knowledge. The afflicted machines essentially become "zombies" in that they only obey their hijacker.

To worsen the situation, these "zombie" networks are being sold or rented to those who are looking for an anonymous way to commit Internet crimes. Some can be rented for only $100 an hour.

"Small groups of young people creating a resource out of a 10-30,000-strong computer network are renting them out to anybody who has the money," said a source in Scotland Yard's computer crime unit.