Sony has a rootkit.
The rootkit phones home.
Phoning home requires a DNS query.
DNS queries are cached.
Caches are externally testable (great paper, Luis!), provided you have a list of all the name servers out there.
It just so happens I have such a list, from the audits I've been running from http://deluvian.doxpara.com .
So what did I find?
Much, much more than I expected.
It now appears that at least 568,200 nameservers have witnessed DNS queries related to the rootkit. How many hosts does this correspond to? Only Sony (and First4Internet) knows...unsurprisingly, they are not particularly communicative. But at that scale, it doesn't take much to make this a multi-million host, worm-scale Incident. The process of discovering this has led to some significant advances in the art of cache snooping. Here are some of the factors I've dealt with . . .
Interesting data, courtesy of Dan Kaminsky.