Check your antivirus program to be sure it’s actually running the scans that I’m sure you have scheduled to occur nightly.
I use Norton Internet Security and I decided to check the scan reports one day and found that my scheduled scans weren’t running. It seems the Windows’ scheduling program interferes on occasion with Norton’s scheduling and for a week Norton was running only the built-in Quick Scan. Yikes!
I immediately ran a full system scan and then started researching why this would happen. Norton, of course, blames Microsoft for the problem but whoever is at fault, the fix is to open the Windows Control Panel and then Scheduled Tasks and then delete the scheduled scan. Then open Norton and reschedule the scan.
Since I learned of this issue, it’s happened on my husband’s computer twice. It hasn’t happened to me again so who knows what triggers the situation.
Computers. Gotta hate ’em.