Capacitive sensing electrodes may be placed in strategic locations inside, outside or inside and outside of a card reader, wherein touch sensor circuitry is then used to take mutual capacitance or self-capacitance measurements that are saved in non-volatile memory as a reference intrusion measurement that is not deleted when power is removed, wherein the reference intrusion measurement may then be used during subsequent intrusion measurements to determine if a skimming device has been disposed adjacent to the card reader, and if a skimming device is detected, appropriate action may be taken such as the automatic disabling of the card reader, the display of a message indicating that the card reader should not be used, or any other action that may prevent a financial card from being compromised.