An inductive security sensor system is not susceptible to magnetic tampering (such as by using an external magnet or false target). A sensor assembly includes an inductive sensor (inductor coil), mounted in a relatively secure location, and a conductive proximity target incorporated with an object (such as a window or door, or an object/asset). An alarm condition can be detected as either a displacement condition in which the proximity target is displaced relative to the inductive sensor, or a tamper condition in which magnetic coupling between the proximity target and the inductive sensor is interfered with (such as by introducing a false conductive target) An inductance-to-data converter drives the inductor coil with an excitation signal to project a time-varying magnetic field for magnetically coupling to the proximity target. The IDC acquires sensor measurements (such as coil inductance), which are converted into corresponding sensor data representing alarm conditions (displacement or tamper).