the following may be hard to believe, read for yourself:
The latest version of ZeuS as of this date is 1.3.4.x and is privately sold. The author has gone to great lengths to protect this version using a Hardware-based Licensing System. The author of Zeus has created a hardware-based licensing system for the Zeus Builder kit that you can only run on one computer. Once you run it, you get a code from the specific computer, and then the author gives you a key just for that computer. This is the first time we have seen this level of control for malware.
http://www.secureworks.com/research/threats/zeus/?threat=zeushttp://www.theregister.co.uk/2010/03/12/new_zeus_features/wonder if you get a discount for two/three PCs