A method for computer security. A gallery comprising a first identity of a first human person is maintained, the first identity associated with a plurality of tags, with first properties, useful for identifying the first human person. A first Internet search for facial images of the first human person is performed using the plurality of tags. A first facial image is selected from the results of this search. A second Internet search is performed for facial images of other human persons based on second properties that are generated by modifying the first properties of the plurality of tags. A plurality of additional facial images of the other human persons retrieved by the second Internet search is selected. A palette of randomized facial images including the first facial image together with the plurality of additional facial images is presented. Access is denied unless the correct facial image is selected.