this post was submitted on 26 Jul 2024
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Lots of dead Lemmy/Kbin domains have CNAME records pointing to the same domain parking company (lemmy.pierre-couy.fr)
submitted 3 months ago by pcouy@lemmy.pierre-couy.fr to c/fediverse@lemmy.ml
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publication croisée depuis : https://lemmy.pierre-couy.fr/post/584644

While monitoring my Pi-Hole logs today, I noticed a bunch of queries for XXXXXX.bodis.com, where XXXXXX are numbers. I saw a few variations for the numbers, each one being queried several times.

Digging further, I found out these queries were caused by CNAME records on domains that look like they used to point to Lemmy/Kbin instances.

From what I understand, domain owners can register a CNAME record to XXXXXX.bodis.com and earn some money from the traffic it receives. I guess that each number variation is a domain owner ID in Bodis' database. I saw between 5 to 10 different number variations, each one being pointed to by a bunch of old Lemmy domains.

This probably means that among actors who snatch expired domains, several of them have taken a specific interest with expired domains of old Lemmy instances. Another hypothesis is that there were a lot of domains registered for hosting Lemmy during the Reddit API debacle (about 1 year ago), which started expiring recently.

Are there any other instance admins who noticed the same thing ? Is any of my two hypothesis more plausible than the other ? Should we worry about this trend ?

Anyway, I hope this at least serves as a reminder to not let our domains expire ;)

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[–] pcouy@lemmy.pierre-couy.fr 1 points 3 months ago* (last edited 3 months ago) (1 children)

These services usually use either or both of passive DNS replication (running public recursive DNS resolvers and logging lookup that returns a record) and certificate transparency logs (where certificate authorities publish the domain names for which they issue certificates). A lot of my subdomains are missing from these services

[–] Ghoelian@lemmy.dbzer0.com 1 points 3 months ago* (last edited 3 months ago) (1 children)

Ahh I guess they probably got my subdomains from let's encrypt then, used them for pretty much all my websites.

Edit: Just checked and yup, all my old subdomains are there from let's encrypt.

[–] pcouy@lemmy.pierre-couy.fr 2 points 3 months ago

What I did is use a wildcard subdomain and certificate. This way, only pierre-couy.fr and *.pierre-couy.fr ever show up in the transparency logs. Since I'm using pi-hole with carefully chosen upstream DNS servers, passive DNS replication services do not seem to pick up my subdomains (but even subdomains I share with some relatives who probably use their ISP's default DNS do not show up)

This obviously only works if all your subdomains go to the same IP. I've achieved something similar to cloudflare tunnels using a combination of nginx and wireguard on a cheap VPS (I want to write a tutorial about this when I find some time). One side benefit of this setup is that I usually don't need to fiddle with my DNS zone to set up a new subdomains : all I need to do is add a new nginx config file with a server section.

Some scanners will still try to brute-force subdomains. I simply block any IP that hits my VPS with a Host header containing a subdomain I did not configure