Looks up IP addresses and domain names in so-called "DNSRBLs". I say "so-called" because there's no real reason why they should be block lists.
This project takes significant inspiration (but no code) from https://github.com/logic/rblcheck. The biggest benefit over the original is IPv6 support, which is unfortunately lacking from most RBL tooling. We also support allow-lists, and if an IP or name is found in one of the allow-lists then we report not blocked. There's no short-circuiting, we'll check all the lists for both IPs and Names, and also check all the block-lists even if we found an entry in an allow-list.
There are currently no lists in the "standard" set, and the SpamHaus key doesn't actually do anything: watch this space.
``` $ dabl --help dabl 0.1.0 Andrew Aylett andrew@aylett.co.uk Queries DNS Allow- or Block-Lists
USAGE: dabl [FLAGS] [OPTIONS] [--] [query]...
FLAGS: --standard Use the built-in 'standard' set of lists -h, --help Prints help information -V, --version Prints version information
OPTIONS:
-a, --allow
ARGS:
The Author uses dabl to restrict access to his IMAP service using TCP Wrappers.
Regular DNSBLs aren't intended to restrict access to consumer-facing services; you probably don't want to block the "Dial-Up Address List", for example.
Spamhaus has a subscription list called "AuthBL" which contains IPs observed attempting credential stuffing.
I have no interest apart from being a very happy user of their free subscription.
Adding this line to /etc/hosts.allow and enabling the relevant configuration in your service will let you query the lists of your choice.
imap, imaps: ALL: aclexec /usr/local/bin/dabl -a al.aylett.co.uk -b bl.aylett.co.uk -b YOUR_KEY_HERE.authbl.dq.spamhaus.net %a
Note that the Author's allow and block lists are not general-purpose, and you'll need a key for SpamHaus. Copy and paste at your own risk! If you want to run your own DNS allow- and block-lists, you may find rbldnsd to be useful.