Dealing with portscans

Grant Peel gpeel at
Mon Sep 22 20:44:48 UTC 2008

----- Original Message ----- 
From: "David Allen" <the.real.david.allen at>
To: <freebsd-questions at>
Sent: Monday, September 22, 2008 4:06 PM
Subject: Re: Dealing with portscans

> On 9/22/08, Greg Larkin <glarkin at> wrote:
>> David Allen wrote:
>>> Over the last few weeks I've been getting numerous ports scans, each 
>>> from
>>> unique hosts.  The situation is more of an annoyance than anything else,
>>> but I would prefer not seeing or having to deal with an extra 20-30K
>>> entries in my logs as was the case recently.
>>> I use pf for firewalling, and while it does offer different methods
>>> (max-src-conn, max-src-conn-rate, etc.) for dealing with abusive hosts, 
>>> it
>>> doesn't seem to offer much in the way of dealing with repeated blocked
>>> (non-stateful) connection attempts from a given host.
>>> Short of running something like snort, is there a suitable tool for
>>> dealing with this?  If not, I'll probably resort to running a cronjob to
>>> parse the logfile and add the offending hosts manually.
>> Hi David,
>> You might want to try security/portsentry from the ports tree.  It's a
>> bit dated, and it has no maintainer at the moment, but a cursory glance
>> at it tells me it might work for you.  It supports pf for blocking
>> connections once your trigger conditions are met.
> I'll give it a try.
> FWIW, I did discover that parsing the log files to get a list of
> offending hosts (denied a number of times above a given certain
> threshold) wasn't really as slow or troublesome as I thought.  That
> slightly hackish approach might be useful for port scans in addition
> to the various rubbish I get sent.
> Thanks to both you and Jeff Laine for the replies.
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Would it work with IPFW or just PF?

Can PF and IPFW run at the same time?


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