Virus protection please? Or is it a scam??

Hi That is a scam messsage - probably from a pop up on a dodgy or compromised website, or from spam email.

You should ignore it.

DO NOT CLICK INSTALL. If you have clicked on any links on the message, and put in any date (eg usernames or passwords) then the scammers have those details and you need to change the passwords immediately.7

See - recognise phishing and other scams:

https://support.apple.com/en-us/HT204759

100% scam. Close the offending page and avoid sites that are involved in such bogus advertising tactics.

go to Settings > Calendar > Accounts and delete the spam account

Go to Settings > Calendar > Accounts and delete the one that has been added that you don’t recognize.

It is a scam.