Five german/french researchers wrote up this very interesting doc (9 page PDF!) called “Measurements and Mitigation of Peer-to-Peer-based Botnets: A Case Study on StormWorm” about one of the biggest and most persistent botnets out in the wild: Storm. It is used for spam and DDOS attacks, has up to 40,000 daily peers and the country hosting the largest amount of bots is the USA.

Anyway, their story on how it works, how they work on infecting new clients, how the researchers worked to infect it and disrupt the botnet communication is a good read.