The "cyberattack" wasn't directed solely at Taleworlds, but was directed at the master servers of multiple games. It just seems like the Taleworlds authentication server (probably hosted on the same box(s) as everything else since their forums were fucked too) was the hardest hit. Valve servers were hit as well as others, but they probably had more intense security in place.
Yeah, it is asinine to think you could "counter-hack" (???) whoever is probably using a botnet to throw shit packets at servers as an individual, but if you just don't know how2computer, I can see where it would be reasonable to think that.