The information contained in your credit card is vital and can be stolen and used in a transaction. The thief will succeed by photocopying receipts or using a skimmer which is an electronic device to replicate and come up with a repository for many credit card numbers. It is always advisable to take care of your credit card wherever and mostly when in social places especially clubs because the moment it goes missing, the thief could access it and skim it.
ATMs are other points where skimming takes place. The thief will set a device in the slot and replicate the data contained in your card and a pinhole camera is put in place to capture your pin number unknowingly as you transact.
Detecting skimming by the card user is quite difficult but the issuer can do that quite easily. The issuer will collect all those cards which have had fraudulent complains in the past and do some data mining to master trends of the merchants. The only way to evict skimming is via strict penalties like banning some of these merchants from the use of credit card which could be a big shock to their business.