Due to the ability of malware to mutate after infection, standard anti-virus signatures may not be able to catch new strains or variants of the malware. Typically, these strains and variants will share unique characteristics with others in their virus family. By using a generic signature to detect the shared characteristics, using wildcards where differences lie, the generic signature can detect viruses even if they are padded with extra, meaningless code. This method of detection is Heuristic detection.