Deleting a subdomain

Our site was hacked by someone that was able to create a new subdomain and point it to a webserver containing their content files. This affected our Google indexing and ranking, and we are trying to resolve this problem in accordance with advice from people assisting on the Google webmasters forum. Here is what we’ve been told: "That subdomain must be deleted correctly and respond 404 to drop out of search. Don’t just remove the DNS as that just says cannot be accessed - delete the subdomain itself."

We have configured a temporary web server that responds with a 404 to any request for content on the subdomain that was created. Can someone explain how it’s possible to respond with a 404 if we have to “delete the subdomain itself”? This seems contradictory. Thanks.

That’s something they would have to explain. I’m pretty sure you’ve figured out how to remove your subdomain from Cloudflare DNS, so you don’t need our help with that. Beyond that, you’d have to ask them for clarification and suggestions on the best way to add a 404 to your server for that subdomain.