Malware authors are acutely aware of their need to maintain the FUD (Fully Undetectable) status, as it is commonly referred to in the malware world, of the malware they create, for as long as possible. The longer the malware perpetrators can delay detection of their malware by security products, the longer they can keep reaping their ill gotten gains from infiltrating their victims. Security products have over the years come to incorporate detection methods to identify these attempts to evade detection.”]
Source: https://securityintelligence.com/malware-authors-fud-fully-undetectable/