If you would like to know a little bit more on botnets and how they actually look like, there is a researcher who actually draw a map of one: What a Botnet Looks Like
About the author
Roger Halbheer is an Executive Security Advisor at Microsoft in EMEA acting as a trusted advisor to CxO. Before that he was a Managing Director at Accenture's Financial Services. Before joining Accenture, he was the Chief Security Officer of Swisscom (Switzerland's largest telecom provider) and the global Chief Security Advisor for Microsoft.