Virus warning

Read Phony "tech support" / "ransomware" popups and web pages - Apple Community for a description of these scams and what to do about them.

This looks like a phishing attempt:

...

Phishing refers to fraudulent attempts to get personal information from you, usually by email. But scammers use any means they can to trick you into sharing information or giving them money, including: 

• Fraudulent emails and other messages that look like they're from legitimate companies, including Apple
• Misleading pop-ups and ads that say your device has a security problem 
• Scam phone calls or voicemails that impersonate Apple Support
• Fake promotions that offer free products and prizes
• Unwanted Calendar invitations and subscriptions

...

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

This is fake, report the hacker/scammer to stop sending. And they steal all your data

Like:

-Your iCloud account data

-Your important files

-etc.

If you get again, just block the hacker/scammer

Hey this would be a fake warning apple would never send you a notification like this I would recommend coming of this site as it could contain viruses