[asterisk-users] SIP Blacklisting

[Cary Fitch]

We would be interested.

Spam is a harder problem to fight due to volume and the ability of any idiot
to set up free email accounts. But anyone blasting SIP systems is a pure
commercial crook. Tagging and strangling them should be a clear cut project.

Cary Fitch


-----Original Message-----
From: asterisk-users-bounces at lists.digium.com
[mailto:asterisk-users-bounces at lists.digium.com] On Behalf Of Steve Howes
Sent: Thursday, October 21, 2010 10:41 AM
To: Asterisk Users Mailing List - Non-Commercial Discussion
Subject: [asterisk-users] SIP Blacklisting

Hi,

Given the recent increase in SIP brute force attacks, I've had a little
idea.

The standard scripts that block after X attempts work well to prevent you
actually being compromised, but once you've been 'found' then the attempts
seem to keep coming for quite some time. Older versions of sipvicious don't
appear to stop once you start sending un-reachables (or straight drops). Now
this isn't a problem for Asterisk, but it does add up in (noticeable)
bandwidth costs - and for people running on lower bandwidth connections. The
tool to crash sipvicious can help this, but very few attackers seem to obey
it..

The only way I can see to alleviate this, is to blacklist hows *before* they
attack. This means you wont ever be targeted past an initial scan.

Is there any interest in a 'shared' blacklist (similar to spam blacklists,
but obviously implemented in a way that is more usable with
Asterisk/iptables)?. Clearly it raises issues about false positives etc, but
requiring reports from more than X hosts should alleviate this. There's all
the usual de-listing / false-listing worries as with any blacklist, but the
SMTP world has solutions we could learn from.

Leaving a 'honeypot' running on a single IP address has revealed a few
hundred addresses in less than a month. I am fairly certain these are all
'bad' as this host isn't used for anything else. There is obviously a wealth
of data (and attacks) out there that would be good to share.

Anyone have any thoughts?

S
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