[gentoo-security] help blocking automated ssh scanning attack script

[Brian G. Peterson]

I've noticed over the last few months that ssh attack scanning scripts have 
been proliferating.  The scripts attack using a common set of usernames with 
weak password combinations, and result in a long line of log entries like:

Nov  6 17:44:18 ethos sshd[3808]: Illegal user test from 211.185.202.3
Nov  6 23:06:27 ethos sshd[8521]: Illegal user rolo from 222.47.83.41

The common usernames are admin root webmaster data rolo guest test patrick 
iceuser www horde wwwrun cyrus courier www-data irc jane pamela cosmin cip51 
cip52 sybase oracle mysql master account server henry frank adam george 
(included here for easier googling on the problem)

I use the excellent portsentry to detect and shut down IP's that do 
traditional nmap-style portscans of my machines.  This attack script isn't a 
port scan, so it just shows up in my security log summaries every morning.  

Can anyone help me out with a simple log scanning script that could detect the 
'illegal user xxx' strings in /var/log/secure and issue the 
"/sbin/iptables -I INPUT -s 221.232.128.2 -j DROP" command to shut these 
addresses down.

The scan volume is up to about two a day on each of my servers, and I'd like 
to get this crap out of my logs

Any assistance appreciated: I and many other people would thank anyone who 
would whip up a script to block this stuff.

Regards,

   - Brian 

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