Malware authors work rigorously to ensure their creations will go undetected by security defenses. Though some adversaries engage in their own hands-on testing, many of them turn to third-party services known as "no-distribute scanners."
Article Link: https://blog.minerva-labs.com/how-can-malware-authors-determine-whether-their-tools-will-be-detected-by-antivirus-solutions