Quick concept overview: mag stripe reader mounted on top of the card insert slot (to capture the card data for later duplication) and a hidden camera mounted
on the side (usually in a form / brochure holder) to record PINs. *UPDATE – here is a site that explains it in detail, with photos.
I heard about this technique a while ago, but today was the first time I’d actually heard from someone (a friend I work with) who experienced it. (Lost $2000 from his account in one day). For you Venturan readers, the hacked machine was the B of A ATM by Mervyns/Baja Fresh (but possibly others in the area as well), so you may want to check your balances.