blacklistd: what does it detect?
norman.gray at glasgow.ac.uk
Thu Apr 23 19:05:35 UTC 2020
On 23 Apr 2020, at 11:24, Norman Gray wrote:
> On 20 Apr 2020, at 12:43, Norman Gray wrote:
>> I've enabled blacklistd on a 12.1 machine accessible to the open
>> internet, but it's not blocking as many failed ssh attempts as I
>> expect. Am I misunderstanding something?
> Is there documentation anywhere (outside of the source) of how
> blacklistd and sshd interact?
> There seems to be very little correlation between what I find in
> auth.log and what blacklistd is acting on, as reported by
> blacklistctl. Addresses seem to be blocked which barely appear in the
> log, and not blocked after making multiple appearances in one message
> or another.
I received an off-list pointer to <https://youtu.be/fuuf8G28mjs> (thank
you!), which is a YouTube video of a good 2015 talk by the blacklistd
developer, Christos Zoulas, talking about the design of the daemon.
There's nothing here which isn't, really, in the other documentation in
the FreeBSD manual and the various manpages, but it provides a very
useful overview of the approach and goals, which has given me, at least,
a much clearer idea of what blacklistd is and isn't doing.
* blacklistd-supporting daemons, such as the sshd in FreeBSD, tell
the blacklistd daemon 'consider blocking this IP' or 'this IP is OK', on
the basis of some criterion compiled into that daemon (ie, there's
nothing to configure here)
* any other logging the (eg) sshd daemon does is for human
information only, and may or may not straightforwardly correspond to
what it said to the blacklistd daemon.
> My immediate goal is to cut down noise in the 'daily security run'
> log, and if that's chattering about connection attempts that
> sshd/blacklistd think aren't worth acting on, then I'm going to feel
> tempted to start fiddling with /etc/periodic/security/800.loginfail
> (which would probably be a bad idea).
...if blacklistd is up and running, then there seems to be a case for
omitting at least some reporting of login failures. How I do that in a
neat and maintainable way is of course a separate question.
Norman Gray : http://www.astro.gla.ac.uk/users/norman/it/
Research IT Coordinator
SUPA School of Physics and Astronomy, University of Glasgow, UK
Charity number SC004401
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