Short for "software robot," as the term is normally used in computer security, a bot is a program that performs a set of malicious actions as instructed by its operator(s). The commands may be scripted or programmed into the bot so that it performs 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 for their communications, although existing or even customized peer-to-peer protocols are sometimes used as well. Peer-to-Peer (P2P)botnets use a more distributed command and control model, so that compromised machines communicate between each other rather than via a C&C server, in order to make the botnet harder to disrupt. The term "bot" may also be used interchangeably with zombie to describe a computer that is infected and controlled by a bot program.