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How do I prevent the following website and similar tools finding subdomains of domains in my server?


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You can add a wildcard DNS record for your domain. Using that, every possible subdomain points at your server. Then your webserver can choose which subdomains have content and which subdomains redirect.

The sites that use DNS records to find subdomains won't be able to distinguish the ones that are used from the ones that are not.

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Oh, that's a great work around! +1 – Simon Hayter Aug 2 '14 at 8:23

You can't due to the nature how sub domains work. When adding a sub domain you are adding public records to the main domain and anyone can do a NS lookup or similar to reveal additional information regarding the domain.

If you want it private then use an internal domain over a VPN or use the IP address, or better yet just ensure your sub domain is secure and not worry.

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AFAIK, finding a list of arbitrary subdomains is not necessarily as trivial as doing a DNS lookup, unless the server responds to AXFR (zone transfer) requests (which most don't)? – w3dk Aug 2 '14 at 11:10

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