Device and Process for anti-theft prevention of a vehicle whith immobilizer

Measurement values, indicating regular vehicle operation in a predetermined time before starting the car, are determined. A decision (7,8) is made if a measured value indicates regular operation before starting the car. The car is started without authentication procedure if the car was previously operated in a regular manner, and with authentication procedure if the car was not previously operated in a regular manner. An Independent claim is also provided for an arrangement for securing a motor vehicle.