CCleaner just became worse. The popular system-cleaning tool now always runs in the background, nagging you and reporting anonymous data back to the company’s servers. We don’t recommend you upgrade
I've always recommended using Microsofts' Defender. This just reinforces the decision I made many years ago.
Watch my video, as I explain how to set this up and why. Go here for more info re virus protection. https://youtu.be/b8KS75MIIzQ