How can I determine if my Mac is being Hacked?

You aren't being hacked. You are being presented with a scam. Do not interact with the message or its criminal sender in any way. Do not click on any links, call any phone numbers, or give any information to the scammers.

FTC – How To Spot, Avoid, and Report Tech Support Scams

FTC – How to Recognize and Avoid Phishing Scams

Recognize and avoid phishing messages, phony support calls, and other scams - Apple Support

If this message is popping up in the upper right hand corner of your Mac's screen, see

Stop unwanted Notifications - Apple Community

It's written for Safari, but the same principles apply if you're using other Web browsers.

get your device scanned