Krebs on Security has a round-up of some of the miniaturized fraud devices that have been found in cash machines so far this year—and it's pretty grim reading. While many card skimmers sit on the outside of an ATM, there's an increasing trend for using devices that are so small, such as the ones below, that they're hidden inside the card slot.
The European ATM Security Team claims that these new insert skimmers are getting harder and harder to detect. In fact, that skimmer was used in conjunction with a tiny camera supported by a rather meaty battery (pictured below) which will keep it running as long as possible. Krebs explains how it works: