Updates KB4556799 and/or KB4501374 switched back to S-mode

Be sure to set a System restore point now. System Restore is your first line of defense if Windows ever malfunctions as it can run even from recovery media to get you back before a problem started. It should always be turned on C drive with plenty of disk space (5-15%) configured. Here's how to check and when necessary how to run System Restore: https://www.windowscentral.com/how-use-system-r...

I'd also get it all set up and when it's running best, save a System Image backup stored externally so if Windows ever becomes irreparable you can restore C in 20 minutes and be up and running. Here's the best free imaging app and how to use it: https://www.howtogeek.com/howto/7363/macrium-re...

I would also use built-in Defender which gives adequate protection, best Windows performance, least issues, and is from Microsoft who knows how to protect their OS best. We see a lot of problems with 3rd party antivirus solutions, almost none with Defender.

If you want the best on-demand scanner install and run Malwarebytes free scanner. https://www.malwarebytes.com/mwb-download/. You can turn off the free trial in Account Settings to keep it only as a free scanner.

Look over the steps for a gold standard Clean Install in this link which compiles the best possible Install of Windows which will stay that way as long as you stick with the tools and methods given, has zero reported problems, and is better than any amount of money could buy: http://answers.microsoft.com/en-us/windows/wiki...

Even if you don't do it, it covers everything that works best in Windows 10 in an install that never has any return problems by those who follow it closely.