[doctorderp]

Sounds like they're just checking if you've visited known cheat sites. Unfortunately the DNS cache is a stupid way to do this since it's open to abuse. Modern browsers will prefetch DNS, so all you'd need to do is put a URL to a known cheat site as a comment somewhere popular in order to get users flagged. Even easier for forums that allow image hotlinking.

A similar thing was done with PunkBuster: https://en.wikipedia.org/wiki/Punkbuster#Attacks_on_PunkBust... - since it was scanning all of your computer's memory for cheat signatures, you could just paste a fragment on IRC in order to get people banned.

[drdaeman]

You could pull the same trick with Battleye, too (it scans all processes' memory for a short list of signatures, too, and several months ago those were leaked).