Brian Krebs tracked down a black-market retailer of mobile-phone-based ATM skimmers that capture your PIN and transmit it to fraudsters over the GSM network. The vendor gave him the whole sales-pitch for the efficiency and safety (for the criminals) of GSM-based skimmers. It's a fascinating read, unless you use ATMs, in which case, it's a terrifying one.
So we potentially have already about 20k dollars. Also imagine that if was not GSM sending SMS and to receive tracks it would be necessary to take the equipment from ATM, and during this moment, at 15:00 there comes police and takes off the equipment.
And what now? All operation and your money f#@!&$ up? It would be shame!! Yes? And with GSM the equipment we have the following: Even if there comes police and takes off the equipment, tracks are already on your computer. That means they are already yours, and also mean this potential 20k can be cash out asap. In that case you lose only the equipment, but the earned tracks already sent. Otherwise without dumps transfer – you lose equipment, and tracks, and money.
That's not all: There is one more important part. We had few times that the police has seen the device, and does not take it off, black jeeps stays and observe, and being replaced by each hour. But the equipment still not removed. They believe that our man will come for it. And our observers see this circus, and together with it holders go as usual, and tracks come with PINs as usual.