I have a virus that the scan can't detect
That is not a virus; it is adware. Adware is a type of software that generates revenue by automatically displaying online advertisements in the user interface or on the screen during the installation process.
Kindly check the links stated below
https://www.mcafee.com/support/s/article/000001899?language=en_US
https://www.bitdefender.com/consumer/support/answer/2574/?srsltid=AfmBOopeeYOcRsFmopd-Blhyh8pxDHwBvJ-CzFs6wAAZhuFF8a8c5CsO
https://malwaretips.com/blogs/beware-of-the-mcafee-safety-warning-pop-up-scam/
https://malwaretips.com/blogs/remove-fake-mcafee-pop-up-virus/
Regards