We blogged about a parallel Zeusbot/Spyeye build near the end of last year that introduced some improvements in the botnet, moving the network architecture away from a simple bot-to-C&C system and introducing the beginnings of a peer-to-peer model.
Source: http://www.symantec.com/connect/blogs/zeusbotspyeye-p2p-updated-fortifying-botnet Andrea Lelli