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How are people discovering random subdomains on my server? (lemmy.blahaj.zone)
submitted 10 months ago by to c/selfhosted@lemmy.world
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I generated 16 character (upper/lower) subdomain and set up a virtual host for it in Apache, and within an hour was seeing vulnerability scans.

How are folks digging this up? What's the strategy to avoid this?

I am serving it all with a single wildcard SSL cert, if that's relevant.

Thanks

Edit:

  • I am using a single wildcard cert, with no subdomains attached/embedded/however those work
  • I don’t have any subdomains registered with DNS.
  • I attempted dig axfr example.com @ns1.example.com returned zone transfer DENIED

Edit 2: I'm left wondering, is there an apache endpoint that returns all configured virtual hosts?

Edit 3: I'm going to go through this hardening guide and try against with a new random subdomain https://www.tecmint.com/apache-security-tips/

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[–] 33 points 10 months ago* (6 children)

For anyone who needs to read it: At the end of the day this is obscurity, not security; however obscurity is a good secondary defense because it buys time.

I too would be interested to learn how this leaked

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  • [–] 13 points 10 months ago (2 children)

    it's not even obscurity; it's logged publicly.

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  • [–] 12 points 10 months ago

    How is it being logged publicly? Like OP said there is no specific subdomain registered in the DNS records (instead using a wildcard). Same for the SSL cert. Only things I can think of is the browser leaking the subdomains (through google or Microsoft) or the DNS queries themselves being logged and leaked. (Possibly by the ISP inspecting the traffic or logging and leaking on their own DNS servers?). I would hardly call either of those public.

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  • [–] 1 point 10 months ago (2 children)

    Isnt security mostly achieved by heavy obscurity? A password secures because other people dont know what it is, it is obscured.

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  • [–] 7 points 10 months ago

    They're not the same.

    Hiding an unlocked treasure chest in the forest is obscurity. Sure, you might be the only one who knows it's there at first but eventually someone might come across it.

    Having a vault at a bank branch is security - everyone knows there's a vault there, but you'll be damned if you're going to get into it when you're not authorized.

    Good passwords, when implemented correctly, use hashing (one way encryption) to provide security. It's not obscured, people know you need a password to access the thing (in our example)

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  • [–] 3 points 10 months ago

    In cryptography, there’s a difference between “secrets” (like passwords and encryption keys), and hiding / obscuring something (like steganography or changing your web server to run on a different port)

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