Records pointing nowhere.

How it happens

You point a subdomain at a hosted service. A help centre, a landing page builder, a status page, a file bucket, a campaign tool. Later you stop using that service and cancel the account. The subdomain record stays where it is, because removing it is a separate action nobody thinks of.

The service provider now has an unclaimed name on their side, and your DNS is still directing visitors to it.

Why it matters

With several major providers, the name you released can be claimed by another account. Whoever claims it controls what is served at your subdomain. That means content on your domain, often with a valid certificate, that you did not publish and cannot remove without changing DNS.

The practical uses for that are phishing that looks entirely legitimate, since it genuinely is on your domain, and cookie or session access if your main site scopes anything to the parent domain.

Why it is so common

• Creating the record and cancelling the service are done by different people at different times
• Nothing breaks visibly when the service goes away, so nobody investigates
• Nobody maintains a list of which subdomains point at which external services
• Trials in particular get set up, forgotten and expired without any cleanup

How to close one

The fix is to delete the DNS record, not to reclaim the service. If you still want the subdomain, point it somewhere you control before you remove anything.

The harder part is finding them, since by definition these are names nobody remembers. That requires enumerating what actually resolves rather than reading a list you already have.

The ongoing version

A single audit closes what exists today. New ones appear whenever a service is trialled and dropped, which is why this is worth watching rather than fixing once. It is also why we alert immediately on this specific finding rather than waiting for the weekly email.