Have Norton 360 but computer hacked. I do updates and scans several times a day. How can it be hacked?

I have Norton 360 on my computers and do several live updates and scans daily. Yet one of my computers was hacked. How can this be? What else do I need to do to prevent this? The issue became apparent today after I upgraded to Windows 10. Microsoft is helping resolve the issue and adding anti-hacking software to my computer that was hacked for $$. Anyone have ideas on how to prevent this in the future on my other computer without having to buy more software protection? I thought Norton 360 was supposed to stop this. A few days ago I even ran the "Power Eraser" and it said all was ok.