ATM scammers are getting more technically adept and have developed a skimmer that has no physical presence on the exterior of the ATM. What they’ve managed to do is create a skimmer so thin it slides inside the actual card slot, rendering it invisible.
On its own the skimmer is only capable of reading the magnetic stripe on the rear of the card. For that data to be usable the PIN also needs to be collected, which will require another device be fitted to the machine. However, splitting the two means the scammer has multiple options (cover the keypad or install a camera) and less hardware to hide on the exterior where it is more easily spotted.