How to protect MacBook Air from online threats?

If these are sliding in the from the top right of the screen, a site you visited has given itself permission to send push notifications. Everything you're seeing is nothing but a scam.

Open Safari's preferences. Click on the Websites tab and then scroll down to Notifications. Clear any entries in the right hand window. You might find something similar in the Pop-up Windows heading below that. Block any you don't recognize.

Then if you want, uncheck the box below as shown here.

I personally can't think of any reason why I would ever want any website to push notices to me.

I cannot thank you enough. It worked very easily.

While almost all of these scam notices are caused by notification links in Safari's preferences, a handful are caused by third party apps that have added themselves to the System Settings. I generally don't mention that as it's pretty rare. Go to:

System Settings > Notifications

In the right column, click on each entry and either disable the entire app's notifications, or do it selectively. Personally, I turn darn near everything off.

Do not bother to uncheck or deny. Just click on it and go to the bottom of box and click on delete

I have never heard of a choice that must be deliberately changed by the user changing itself back.

I presume you're talking about the option that is unchecked in the image, and not the one at the lower left?

As you suspect, all such messages are scams presented by criminals. Please see the user tip below for steps to deal with the bogus notifications.

Stop unwanted Notifications - Apple Community

I did uncheck the box, but if I leave that section to look at something else and go back it is checked again. How can I delete it?

I had this exact same issue, I even had two of the same thing with allowed notifications.