Lie to an employer about your facebook?

okay so do big companys really have programs to see your facebook even if youve set it so no one can search for you and only your friends can see your profile? I am going for an interview and i feel like they will ask if i have a facebook, i do and it has somethings i wouldnt want my employer to see....its not under my real name but i feel like what if they find it and are like *she lied* thats not good.........what should i say if they ask if i have one?