A method of and a system for warning about an unauthorized object attached to a bottom part of the vehicle includes storing images of vehicles or the data corresponding to the images in server means, examining a bottom of a vehicle by image producing means, transmitting from the image producing means an image of a bottom of a vehicle or the data corresponding to the images to the server means, comparing the transmitted images of the bottom of the vehicle or the data corresponding to the images with a stored image of a bottom of a corresponding vehicle or the data corresponding to the images, and producing a signal indicative of whether the bottom of the examined vehicle contains an unauthorized object or does not contain an unauthorized object.