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From: Danny Pansters <danny@ricin.com>
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Date: Thu, 4 Mar 2004 02:16:03 +0100
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Subject: Re: ipfw rules
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On Thursday 04 March 2004 01:42, RYAN vAN GINNEKEN wrote:
> I know this has probably been posted 1000's of times but i would like to
> set up a ipfw firewall i run many services on this machine. It acts as a
> gateway for my network
> APACHE web server
80/TCP and perhaps 443/TCP
> IMAP mail server
143/TCP
> SMTP  mail server
25/TCP
> BIND name server
53/UDP for xfers 53/TCP
> FTP server
21/TCP
20/TCP maybe

(I use ipf but the principles are the same)

- block in/out packages you never want to see at all (e.g. with weird opts or 
too short to be normal)
- block in anything from your own IP
- block in anything from private addresses (you can get and update lists of 
these)
- let no broadcasting packets come in or go out even on wrong bcast addresses
- block in (and log) everything else except:
- your services on their ports keep state and with proxy if needed (ftp?)

- let everything outward go and keep state or:
- let nothing out except what you may initialize (and keep state) e.g. web 
traffic, mail retrieval, etc. More cumbersome.

- decide on ping etc, what do you want to come in and what ICMP do you want to 
respond to
- send out resets rather than ICMP-no-answer or whatever it's called on 
blocked ports

Keep huge big logs at first, then later strip out what you know means no harm. 
I don't know about VNC.


HTH,

Dan