According to the card reading device (20) for a self-service terminal comprising a intake compartment (13) for a card (11) containing data to be read, wherein the self-service terminal comprises at least one sensor (6A, 6B) and an evaluator device connected hereto and the card reading device (20) is protected against manipulation attempts by arranging at least one sensor in the card reading device (20) and at least one linearly extending sensor arrangement (6A,6B) that is attached in the intake compartment (13), wherein the evaluator device (4) checks at least one spatial dimension (1,b) of the card via the sensor arrangement (6A, 6B). Preferably the sensor system is a sensor arrangement comprising a plurality of linearly extending sensor elements that extend in a first direction (X) or a second direction (Y) in relation to the card (11) retracted into the intake compartment (13). Thereby it can be effectively determined whether a retracted card is a genuine card of if a manipulation is present that targets the inside of the card reading device.