Anti-spoofing technology is provided for verifying a user of a fixed computer terminal. Image data of at least one verification image is received, as captured by an image capture device of the fixed computer terminal at a time corresponding to a request for access to a restricted function of the fixed computer terminal. User verification is applied to determine whether to grant access to the restricted function of the fixed computer terminal. A differential feature descriptor is determined, which encodes feature differences between the verification image data and image data of at least one unobstructed background image as captured by the image capture device. An anti-spoofing classifier processes the differential feature descriptor to classify it in relation to real and spoofing classes. Access to the restricted function of the fixed computer terminal is refused or granted based on the classification of the differential feature descriptor by the anti-spoofing classifier.