Botnets are widely regarded as the top threat to network security. This paper explains how botnets have traditionally worked, then contrasts the established model with startling botnet innovations that emerged in 2007 and are continuing to evolve. Examples describe botnets known as Zunker, Gozi, Storm, MayDay, and a kit known as Mpack that helps botmasters easily create malicious web sites. After explaining why the latest innovations make bots a more serious threat than ever, the paper concludes by suggesting defensive countermeasures.