1. A computer program product having a computer program for controlling a computer to detect computer data containing compressed video data as being banned computer data, said computer program product comprising: identifier reading code operable to read from said computer data an identifier of a decoder operable to decompress said compressed video data; identifier comparing code operable to compare said identifier with one or more predetermined characteristics indicative of whether said identifier is associated with banned computer data; and triggering code operable if said identifier is associated with banned computer data, to trigger a banned computer data action.