Anti-theft device for a motor vehicle

A device for anti-theft protection of a motor vehicle is proposed. At least one signal processing unit (14) evaluates a sensor signal (12) from a sensor (10) in a first operating mode (16) for generating an activation signal for a functional unit (21, 22, 24). A signal unit (14) evaluates the sensor signal (12) in a second operating mode (18), which differs from the first operating mode (16), for generating an activation signal for an alarm signal generator (26). An operating state detection device (28) is provided for detecting whether the motor vehicle (40) is in a deactivated state. The second operating mode (18) is activated when the motor vehicle (30) is in the deactivated state; the first operating mode (16) is activated when the motor vehicle (30) is in the activated state.