Deep Skimmers

It was generally thought that captive card readers were more secure because they had a motorized reader (card grabber) and shutter that wouldn't allow a skimmer to be inserted. Now there are "deep insert" skimmers that can bypass that mechanical obstruction.

From Krebs on Security:

ATM maker NCR Corp. says it is seeing a rapid rise in reports of what it calls “deep insert skimmers,” wafer-thin fraud devices made to be hidden inside of the card acceptance slot on a cash machine.