From 2-spyware.com
Win64:malware-gen is a detection name for a type of malware known as a Trojan. Trojans are among one of the most prevalent and versatile threats around, as their nature and working mechanisms can deffer vastly, although all of them have one thing in common; users get infected with a Trojan when they open a malicious file, believing that it is actually legitimate, e.g., a software crack or a spam email attachment.