@Ste1lar@niu.moe Linux, nothing as long as your not recklessly using root or granting permissions.

Windows, the built in Windows Defender. I talked enough with honest AV developers before, for the good of all security, each AV company reports back into central shared databases on threats and fixes. So on a worst-case zero day, the AV company that finds/fixes may have a few hours lead before everyone else has it...

That being said...just don't use Windows unless forced :P