What is botnet and how does it spread?

Описание: Malware or malicious computer code has been around in some form or other for over 40 years, but the use of malware to take control of a group of computers that are then organized into something called a botnet is more a twenty-first century phenomenon. Botnets have been responsible for some of the most costly security incidents experienced during the last 10 years, so a lot of effort goes into defeating botnet malware and, when possible, shutting botnets down.