Generally speaking, there are not TOO many hacks for world of warcraft because all the data is stored server side, if you dont know what that means, basically everything that is worth hacking, for example your level, is stored on the servers database, which means no hack can change it as you cant get access to a external database usually.

However there ARE some hacks that for example allow you to fly around the map or go through walls, and these are done through VERY rare exploits that are sometimes found, most of these are fixed very quickly, there are a few sites that offer these for free download, but i cant give the link out, and most other sites are fake.