Abstract: The invention relates to a sensor, in particular for detecting attacks on at least one signal-carrying line (11), in particular of chip cards (1), said sensor having a circuit arrangement (10) which comprises a first circuit arrangement (13) for detecting an instantaneous voltage value above a first supply voltage and a second circuit arrangement (14) for detecting an instantaneous voltage value below a second supply voltage, wherein, when a voltage value outside the range between the first and second supply voltages is detected, a signal (19) is generated and can be taken as a basis for initiating a protective measure.