What is a Bot ? - Security Term

A bot is a compromised computer which is running software that allows a remote computer to control it. The software is usually installed by someone breaking into the computer, but can also be installed by a user who thinks he is installing a game or other software which he may have downloaded from a website or received via Instant Messenger (IM). Just like worms, bots can duplicate inside computer networks and can cause 'traffic jams' in those networks. Unlike worms that exploit existing vulnerabilities, bots create their own by opening up backdoors, which are holes in your security, in order to control your computer so that the hacker can steal your information, spy on you, relay spam email using your IP address, and launch those same attacks on other computers in the network.