McAfee and iMac Firewalls

There is no reason to ever install or run any 3rd party "cleaning", "optimizing", "speed-up", anti-virus, VPN or security apps on your Mac.  This user tip describes what you need to know and do in order to protect your Mac: Effective defenses against malware and other threats - Apple Community.  

Uninstall the McAfee software according to the developer's instructions.

The best antivirus, cleaning app, and overall maintenance app for Mac OS is Mac OS itself. All you need to do with Mac OS to keep it secure and running well is to keep it up-to-date and do periodic (about 1x per week) restarts. Other than that, leave it alone. Adding third party antivirus, cleaning, security and other types of maintenance apps to Mac OS adds no additional level of security. The only thing these apps do is have the opposite affect users want. They make Mac OS slow, unstable, generate odd behavior (much like you are experiencing) and make Mac OS appear buggy.

Please locate the developers uninstall instructions for McAfee and follow to the letter. Then restart in Safe Mode per the directions in Use safe mode to isolate issues with your Mac and then restart normally.

I agree 100% with the others. Don't ever install McAfee. If it is installed, delete it according to McAfee instructions.

Cheers,

Jack

I'd remove McAfee entirely, and use backups and the built-in macOS security.

Some related reading > Effective defenses against malware and other threats - Apple Community

McAfee serves absolutely no purpose on a Mac other than to slow it down, interfere with normal processing, and take your money.

Uninstall it.

Agree. I administer Macs here at our company and 3rd-party firewalls/AV products do more harm than good. Remove McAfee entirely and watch the performance of your Mac improve. It is of no use.