Modern, popular software like Sylenth1 uses complex, online-activated licensing systems. A keygen is often ineffective against cloud-based licensing, making a truly "new" keygen that works on the latest, updated version a rarity, if not a total fabrication.
Security companies like Malwarebytes classify keygens as "CrackTool" or "RiskWare"—items that are not strictly viruses but pose a significant risk to the user. By running a keygen, you are effectively giving potential attackers the keys to your digital identity. sylenth keygen new