Automatic Firewall software?

Paul Schmehl pauls at
Wed Oct 13 09:15:00 PDT 2004

--On Wednesday, October 13, 2004 10:04:24 AM -0400 "Brian J. McGovern" 
<bmcgover at> wrote:
> 	Rather than having to hang over my machine is there any software out
> there that will monitor logs (e.g. /var/log/messages), parse out failed
> logins like this, and run an ipfw command to block it? Perhaps something
> can be done via PAM?
Yes.  Look at the Sentry Tools project at Sourceforge. 
(<>)  In particular, portsentry 
will do exactly what you want.  It will throw up a temporary rule in ipfw 
blocking the host.  (I say temporary because when you restart ipfw it will 
go away.)  It will also add the host to your /etc/hosts.allow file, 
blocking it permanently from accessing privileged services.

> 	An added extra bonus would be if it would unblock after some period
> of time, in case a legit. user bungles their password, and can't get in
> (saves the service call).
It won't do that, but you can just run ipfw show and then delete the rule. 
Then you can add that host to the portsentry.ignore file, and it will never 
happen again.  (Or you can do it proactively if you know the hosts or 
networks your users will be coming from.)

I've been using it for years.  Works very well, but be careful.  On a large 
server with lots of activity, you probably want to start by not blocking 
anything until you're comfortable with your ignore file.

I also use logsentry on a number of hosts.  Very nice program.  Both are 
well written and quite mature.

Paul Schmehl (pauls at
Adjunct Information Security Officer
The University of Texas at Dallas
AVIEN Founding Member

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