Antivirus engines classify KMSPico as HackTool:Win32/AutoKMS or similar. This is Microsoft Defender's way of saying: "This is a tool designed to circumvent licensing. Even if it doesn't contain a traditional virus, its behavior is malicious by definition."
You have better options:
If you must have a genuine activation, you don't need to pay $199. Legitimate resellers offer: kmspico original