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I wasn't able to sign up for postmaster@rootshell.is, but I was able to get abuse@rootshell.is. You should be careful about what standard email addresses you al
by mike-cardwell 4mo ago
I wasn't able to sign up for postmaster@rootshell.is, but I was able to get abuse@rootshell.is. You should be careful about what standard email addresses you allow people to take. I recommend you take abuse@ back from me and you should really have a strong denylist. I just asked an LLM for a list of things you should be blocking and it came back with the following. The cert validation ones seem particularly important:
RFC 2142 mailbox names (the core list):
postmaster@ — required by RFC 5321; mail systems expect it to always work
abuse@ — for reporting spam/misuse
hostmaster@ — DNS issues
webmaster@ — website issues
noc@ — network operations
security@ — security/vulnerability reports
info@, marketing@, sales@, support@ — business functions
TLS/certificate validation addresses (RFC 8552 / CA-Browser Forum):
admin@, administrator@
ssladmin@, ssladministrator@, sysadmin@
These can be used to validate domain control and issue certificates, so handing them to a random user is a real security risk.
Common automated/system senders people impersonate or that cause confusion:
noreply@, no-reply@, donotreply@
mailer-daemon@ — bounce messages (RFC 5321 sender)
root@, daemon@, bin@, sys@ — Unix-style system accounts
null@, devnull@
Brand/trust-sensitive ones worth blocking too:
billing@, accounts@, payments@
help@, contact@, service@
legal@, privacy@, dmca@
register@, registration@, signup@
The service's own name (e.g. [brand]@, team@, staff@, official@)
[edit] Re the TLS issue. You should set up a CAA DNS record and also check on crt.sh later to see if anybody managed to get a cert for rootshell.is if you didn't lock down the validation addresses
- jszymborski 4mo agoI hate shoving LLMs everywhere, but honestly this is probably a good use case for tiny models like the 0.6B Qwen model to flag account names for human review.
- rho138 4mo agoOr just read the RFCs tbh. I keep them indexed locally as text, it’s super useful for finding random garbage that may not pop up from a search.
- jszymborski 4mo agoThere's a lot of stuff that looks officious enough that will trick folks, especially those distracted or not well-versed in the attack vector.
- rho138 4mo ago> not well-versed in the attack vector. Stochastic outputs that may not mesh with reality? xD
- sc0rt 4mo agoI found the guy on X, wasn't that hard: https://x.com/haptagod https://x.com/haptagod You should probably hit him up and tell him these things?
- mike-cardwell 4mo agoI don't use X. You can tell him if you want.
- charcircuit 4mo agoWouldn't the better guidance be to use different domain for official communication similar to sites where you can customize the subdomain? Attackers can always come up with something you didn't think to block. Google doesn't let just anyone make a mail on the google.com domain for example.
- mike-cardwell 4mo agoThat wouldn't be better guidance. That would be additional guidance. I'm sure Google also never let anybody set up postmaster@gmail.com