The Warden is Blizzard's cheat detector for World of Warcraft. It is constantly lurking in the background and the minute you log onto WoW it will check to see if you are running any programs or hacks that you shouldn't be running.
Countermeasures against The Warden are combated by constant switching out of its current version on the server.
Are you willing to take the risk and have your account banned?
For World of Warcraft mods that you can use legally within the game, check out my WoW Mods Guide