RFE: dnsbl-support for dovecot

Reindl Harald h.reindl at thelounge.net
Tue Jun 17 17:56:13 UTC 2014

Am 17.06.2014 19:43, schrieb Giles Coochey:
> On 17/06/2014 18:16, Reindl Harald wrote:
>> after having my own dnsbl feeded by a honeypot and even
>> mod_security supports it for webservers i think dovecot
>> sould support the same to prevent dictionary attacks from
>> known bad hosts, in our case that blacklist is 100%
>> trustable and blocks before SMTP-Auth while normal RBL's
>> are after SASL
>> i admit that i am not a C/C++-programmer, but i think
>> doing the DNS request and in case it has a result block
>> any login attemt should be not too complex
>> setup a own honeypot and feed rbldnsd with the sources
>> is quite easy and in case of a own, trustable RBL where
>> no foreigners report somebody by mistake it's relieable
>> and scales well over many machines and services as long
>> services supporting it
>> mod_security:
>> http://blog.inliniac.net/2007/02/23/blocking-comment-spam-using-modsecurity-and-realtime-blacklists/
> If you have the bllist as a file then you may as well drop with iptables (in Linux) or ipfw (BSD).
> Use an IP tool for an IP block, not the application.
> Spamhaus project has a kind of script for this type of thing:
> http://www.spamhaus.org/faq/section/DROP%20FAQ
> I'm quite happy to use fail2ban, yes - dovecot has to handle a few failed logins for each blocked IP, but it works
> for me and pretty much mitigates the attack

that's not the point, to achieve the same as with a RBL you
need to manipulate iptables on every machine - the RBL is
centrally for HTTP/SMTP and so it makes sense to use
it also for IMAP/POP3

additionally you have no log - thats bad with a RBL you have a
dedicated log containign much more data than source / target IP
and ports

also i don't want to have fail2ban on every machine, the point
of a RBL with a honeypot is that bad machines are blocked
for 7 days just beause they touch any unused IP and likely
before they even hit the production servers

iptables-rules are managed here also centralized over a lot
of machines and i really don't want to marry the honeypot with
the iptables

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