I click the close button of the alert window and the danger is gone.

I configured my antivirus software so, that I don't have to do anything anymore.

I check to see what it is about and I repair or remove the concerning file.

I also use an online scanner on the Internet, to make sure it is not a false positive.

I have no virus scanner.

I call the hotline of my antivirus provider, just as a precaution.