Botnets, which are connected PCs that have been remotely taken over by hackers without their owners knowing, seem to be on the rise. Some botnets contain as many as 50,000 compromised zombie machines, and are seemingly the work of some very skilled and organised people. There may be as many as one million hosts compromised out there.
Just 100 active botnets tracked by Honeynet launched 226 distributed denial of service (DDoS) attacks in a three-month period from November 2004 to January 2005.
One of the botnets contained 50,000 compromised zombie machines. In the three-month tracking period, Honeynet detected 226,585 unique IP addresses joining at least one of the channels being monitored.