Botnet

A Botnet is a network of compromised computers; while not a form of malware, a botnet can be the consequence of a malware attack. Often created by a Trojan horse or a worm, a botnet can be used to send spam or to attack computers. For example, security researchers at Intego discovered a Trojan horse responsible for a Mac botnet in January, 2009, hidden inside pirated copies of popular Mac software.