this invention relates to a method of detecting a presence of a circuit extending arrangement inserted between a physical interface , connected to a terminal , and a smart card , the physical interface being adapted to receive the smart card , the method comprising the steps of measuring at least one electrical characteristic of the physical interface , and determining whether a circuit extending arrangement , changing at least one characteristic of said physical interface , is coupled to said physical interface on the basis said measurement . in this way , simple and efficient detection of a tampering / spy circuit is provided .