Virus??

All such messages are scams. Do not interact with the message or the sender. Never, never, never download anything based on a popup message. Close the offending page and avoid sites that are involved in such bogus advertising tactics.

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

It's a malicious ad designed to scare you into downloading useless software.

Stop going to sites that rely on such scams for money and install an ad blocker.