A method and an apparatus in clamp protection systems (1-3) for doors and eventually existing footsteps (7) co-operating therewith, comprising a digital camera (4) at actual doors (1-3), which camera (4) is connected to a central computer (5) having a monitoring screen (5) to which also the ordinary opening and closing electronic means (6) are connected. Each camera transmits images at short intervals to the monitoring screen (5), each image is frequently compared with a reference image stored in the monitoring screen (5), and whereby alarm is given as soon as an image received from a camera (4) differs from the reference image of the monitoring screen (5), whereby the door (1-3) in question is opened or is maintained closed until the monitoring screen (5) observes that the received image coincides with the reference image.