My theory is to use the oldest operating system that still functions on the internet. If you are that behind the times, no one cares about you enough to exploit you. I'm still using XP, but it is beginning to fail me. I'm considering moving up to Windows 7. Of course, I don't keep any worthwhile data on these "dirtball" computers. The hackers can have their way with me, but they never do. If they did, I'd just re-load. They'd rather take down a Windows 10 or 8.1 system. (If I could run Windows 3.1, I would.)