[cardamomo]

It occurred to me once upon a time that I could use just such a keylogger to capture my classmates' student ID card swipes when they went to release print jobs at any of the print stations on my university campus. I recognized this as a security flaw that (probably) didn't have many lucrative uses, but I never imagined such a technique might work for credit cards. I wrongly assumed that credit card readers would employ greater physical security.

[artas_bartas]

hardware security aside, if credit card readers employ proper encryption, that in itself would probably be an effective deterrent against such leaks, but only IF such encryption is implemented.