A botnet is a number of Internet-connected devices, each of which is running one or more bots. Botnets can be used to perform distributed denial-of-service attack, steal data, send spam, and allows the attacker to access the device and its connection. The owner can control the botnet using command and control software. The word “botnet” is a combination of the words “robot” and “network”. The term is usually used with a negative or malicious connotation.