Countries with the most botnets

[Steven Bellovin <smb () cs columbia edu>]

A colleague needs to know, along with citable sources if possible.

Ideally - number of zombified PCs, percentage of zombified PCs, name of
nation, source.

Threat reports from symantec and macafee suggest the US leads, with
China a very close second.

Yes, we realize that answers will be imperfect.

                --Steve Bellovin, http://www.cs.columbia.edu/~smb