My history shows that every 4 seconds a threat is attempted and blocked?

My laptop has been really slow for awhile so I ran all kinds of scans and optimization tools. Still slow. I checked the Norton recent history and it shows that every 4-5 seconds an "Unauthorized Access" is attempted. I've tried putting my computer back to factory defaults, but I still have the same problem. How do I get this to stop? I also ran the Power Eraser, but it showed no issues.