Countries with the most botnets

[sean at donelan.com (Sean Donelan)]

On Wed, 27 Jan 2010, Steven Bellovin wrote:
> 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.

Data is of course needed as a starting point.  But does anyone have 
anything to explain differences between countries, industries, some other 
distinction, if any?  Although we use terms from biology, i.e. infection, 
virus, etc; bots aren't naturally occuring phenomena.

Or even in small communities, do universities have differences between 
themselves?  Resnets vs faculty?  Engineering vs arts & sciences?