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How are people discovering random subdomains on my server? (lemmy.blahaj.zone)

submitted 5 months ago* (last edited 5 months ago) by BonkTheAnnoyed@lemmy.blahaj.zone 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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[–] ambitiousslab@lemmy.ml 10 points 5 months ago (1 children)

I believe that some DNS servers are configured to allow zone transfers without any kind of authentication. While properly configured servers will whitelist the IPs of secondaries they trust, for those that don't, hackers can simply request a zone transfer and get all subdomains at once.

[–] BonkTheAnnoyed@lemmy.blahaj.zone 12 points 5 months ago

I don't have any subdomains registered with DNS.

I attempted dig axfr example.com @ns1.example.com returned zone transfer DENIED