Botnet

A Botnet (short for robot network) is a word which is sometimes used by computer scientists. Botnets are made up of many software agents. Each software agent is controlled remotely. Botnets are known for their ability to act as a unit.
Such networks are often used to send E-Mail Spam, but they can also be used to attack (and bring down) a computer through Denial of Service attacks, amongst others.
A Botnet can also be referred to as a group of hundreds, thousands, or even tens of thousands of zombie computers that are under the control of an attacker.