Bot

Short for "software robot," as the term is normally used in computer security, a bot is a program that performs malicious actions as instructed by its operator(s).

The commands may be scripted or programmed into the bot to perform actions when certain criteria are met, or the bot may dynamically receive instructions by connecting to one or more Command and Control servers.

Bots that communicate in such a fashion frequently use IRC and HTTP, although existing or customized peer-to-peer protocols are sometimes used. Peer-to-peer (P2P)botnets use a more distributed command and control model so that compromised machines communicate with each other rather than via a C&C server to make the botnet harder to disrupt.

The term "bot" may also be used interchangeably with zombie to describe a computer infected and controlled by a bot program.