What is a Botnet?

A botnet or robot network is a group of computers running a computer application controlled and manipulated only by the owner or the software source. The botnet may refer to a legitimate network of several computers that share program processing amongst them.

Usually though, when people talk about botnets, they are talking about a group of computers infected with the malicious kind of robot software, the bots, which present a security threat to the computer owner. Once the robot software (also known as malicious software or malware) has been successfully installed in a computer, this computer becomes a zombie or a drone, unable to resist the commands of the bot commander.

A botnet may be small or large depending on the complexity and sophistication of the bots used. A large botnet may be composed of ten thousand individual zombies. A small botnet, on the other hand may be composed of only a thousand drones. Usually, the owners of the zombie computers do not know that their computers and their computers' resources are being remotely controlled and exploited by an individual or a group of malware runners through Internet Relay Chat (IRC)

There are various types of malicious bots that have already infected and are continuing to infect the internet. Some bots have their own spreaders - the script that lets them infect other computers (this is the reason why some people dub botnets as computer viruses) - while some smaller types of bots do not have such capabilities.