From owner-freebsd-ipfw@FreeBSD.ORG Sun Nov 27 18:48:49 2005 Return-Path: X-Original-To: freebsd-ipfw@freebsd.org Delivered-To: freebsd-ipfw@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id DE00E16A41F for ; Sun, 27 Nov 2005 18:48:49 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from pi.codefab.com (pi.codefab.com [199.103.21.227]) by mx1.FreeBSD.org (Postfix) with ESMTP id A6FB443D67 for ; Sun, 27 Nov 2005 18:48:46 +0000 (GMT) (envelope-from cswiger@mac.com) Received: from localhost (localhost [127.0.0.1]) by pi.codefab.com (Postfix) with ESMTP id F3FB95FA5; Sun, 27 Nov 2005 13:48:45 -0500 (EST) Received: from pi.codefab.com ([127.0.0.1]) by localhost (pi.codefab.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 60149-04; Sun, 27 Nov 2005 13:48:45 -0500 (EST) Received: from [192.168.1.3] (pool-68-161-122-227.ny325.east.verizon.net [68.161.122.227]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by pi.codefab.com (Postfix) with ESMTP id D15BF5CA1; Sun, 27 Nov 2005 13:48:44 -0500 (EST) Message-ID: <4389FF8D.6050806@mac.com> Date: Sun, 27 Nov 2005 13:48:45 -0500 From: Chuck Swiger Organization: The Courts of Chaos User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.12) Gecko/20050915 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Alexandre DELAY References: In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-Virus-Scanned: amavisd-new at codefab.com Cc: freebsd-ipfw@freebsd.org Subject: Re: Protocol filter capabilities X-BeenThere: freebsd-ipfw@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: IPFW Technical Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 27 Nov 2005 18:48:50 -0000 Alexandre DELAY wrote: [ ...top-posting reformatted... ] >>> Don't you think that it would be a nice thing to be able to include such >>> "filters" from, for example, ethereal? Ethereal support more than 34k >>> different protocols. It woul be nice to be able to choose from those >>> filters and to apply some rules according to those filters. >> >> You're talking about a reactive IDS. You can rig them up using scripts >> which monitor logfiles, or something like /usr/ports/security/snort. >> >> However, I prefer to use IDS for traffic I permit but want to monitor, not >> traffic I already know I want to block. > > Snort doesn't answer to such needs. > It is not able to analyze application protocols such as BEEP or Edonkey. > See: http://www.snort.org/docs/writing_rules/ > > filter application protocol based on ip/ports is not efficient. Some > application are able to work on almost any port. Snort is a tool. It can be used to build an IDS and is well-suited for that task, but it is not intended to entirely replace a firewall. It is true that P2P application protocols are very adaptive and are able to work via almost any port. However, they do not work through a properly configured proxy using a "deny all" firewall in what is called a DMZ or screened subnet firewall architecture. If your network is set up for this correctly, internal machines on the LAN will never be allowed to make external requests, at all (period); clients may even run without a default route set and without the firewall having NAT enabled. -- -Chuck