What is a Botnet?

A botnet is a collection of compromised computers that are directly under the control of a single malicious entity. Computers become compromised once malicious software is installed on them. This malicious software, or malware, is engineered specifically to gain access to and maintain control over the victim machine. Anti-virus companies label this malware as a virus, worm, or a trojan, but these designations are useless when considering the behaviour and capability of a botnet. Modern day malware evolves to become whatever is needed by its controller and is not limited by the boundaries of anti-virus labels.

Once the malware is on the system it seeks communication with its controlling entity. With communication established, any compromised machine can be capable of carrying out any order issued by the botnet controller and any data on the compromised machine can be extracted for use, sale or distribution by the attacker.