Mac quarantine file

Where did you find this Quarantine file? Note that it is normal to find an item called Quarantine.kext (with an executable file inside it named "Quarantine") on a Mac. That is not a part of McAfee, nor should you remove it. It is a part of the system.

I agree with Allan that McAfee is likely the cause of your internet performance issues, and would probably be best removed. However, it is a bit over-simplified to say "there are no Mac viruses." There is malware for the Mac, and one recent discovery exhibits virus-like behavior, installing itself with no user interaction if you have an outdated version of Java. You need to be aware of these threats, otherwise you will not use appropriate caution online. For more information, see my Mac Malware Guide.

(Note that my pages contain links to other pages that promote my services, and this should not be taken as an endorsement of my services by Apple.)

Is it safe to delete since

It won't even let me open it?

As a basic rule, you should avoid attempting to open files which you believe may be a virus or malware. You would generally be required to authenticate with your password before anything would get installed, but attempting to open it in the first place would seem to imply that you thought it would be safe to do so. While there are no viruses in the wild that would infect your Mac, there is nothing to stop you from installing malicious software if you give it permission to do so.

McAfee will serve no useful purpose on your Mac since there are no virus for it to find. The only thing it will do is cause problems. I suggest you uninstall it.

Allan

File or folder? Most anti-virus software create a folder to place quarantined files - files that it thinks are infected. Consult the program's documentation for help.

Yes