http://blog.immunet.com/blog/2010/10/26/the-prevalence-of-threats-how-popular-is-the-malware-that-in.html

In my last blog post, I talked about the infection rates of Immunet users (namely looking at how many threats we blocked on different machines). In this post, I’d like to dive into how frequently a piece of malware might show up on a given system.