But what happens when your Mom walks in and your in the middle of Naxx? You don't think she'd figure out your playing WoW Crack?
Seriously, I have no idea what kind of self check WoW does upon launching to guarantee compatibility with the server, but I'm thinking you'd have to be careful not to flag yourself to Blizzard as a hacker. But that is just a guess.
Login when no one is looking, and load when no one is looking? But seriously, your mum would know it's WOW by looking at it. Just don't play it when your not meant to, it's only a game.