If I register with a dyn DNS service and am allowed to select my own prefix, how secret is the URL?
For example: I register with a dyn DNS service and ask for my prefix to be 204e9800998ecf8427e and the service gives me the URL 204e9800998ecf8427e.some-dyn-dns.org. I configure my home router to tell the service its IP and from then on the URL points to my router.
Given I don't tell anyone about the URL, who will be able to find my router (without using brute force on either an IP or DNS level)? Can the name be looked up in a registry? Can the DNS server of the service be probed to reveal the URL? Does it depend on the service?