You can use iptables to block any string including DNS requests. This is pretty awesome way to block certain domain or dns queries on Linux.
From the blog post:
I have been seeing a lot of weird/bogus DNS traffic (thousands of queries a second) hitting our servers lately and I decided to try and block it. Specifically I saw tons of requests coming in for proxypipe.net with a bunch of random hosts prepended. Things like: 6Gdb1QlP.f.proxypipe.net., mhl00ULG.e.proxypipe.net., clacqxlG.f.proxypipe.net., etc. I decided I would block all DNS requests that contained the “proxypipe.net” anywhere in the packet.