The conflict between malware authors and analysts is heating up as both are coming up with new armaments in their armory. Malware authors are employing novel sophisticated techniques like metamorphosis to thwart detection mechanisms while security professionals are budding new ways to confront them. In this paper we formally treat diverse mechanisms of making malware undetectable in general and code mutation techniques in particular. We also supported our argument where possible, through different tools and have revealed their outcome. In the end we give our methodology to make any virus undetectable using amalgamation of hex editing and metamorphic techniques.