(roBOT NETwork) Also called a "zombie army," a botnet is a large number of compromised computers that are used to create and send spam or viruses or flood a network with messages as a denial of service attack. The computer is compromised via a Trojan that often works by opening an Internet Relay Chat (IRC) channel that waits for commands from the person in control of the botnet. There is a thriving botnet business selling lists of compromised computers to hackers and spammers. See denial of service attack, spambot, zombie and spam 2.0.