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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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[–] Keelhaul@sh.itjust.works 12 points 5 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.