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Re: DMZ / Firewall rule diagramming
From: Michael Gale <michael.gale () bluesuperman com>
Date: Sun, 05 Dec 2004 22:47:20 -0700

Hello,

I understand what you want now ... I don't believe this has every been done as a standard.

Michael.


Craig Humphrey wrote:
Hi Michael,

From the responses I'm getting, I don't think I explained the situation
very well.

I'm not after "how to write rules" or "what rules should I have".  I'm
looking for a generic way to diagram the rules I already have.
Preferably something nice a visual (like Visio), but even Visio starts
to get cumbersome with a complex DMZ, even breaking flows/rules into
layers only goes so far.

I was hoping that the industry had developed some formal standards for
diagramming DMZs and flows/rules.

Thanks
Craig



-----Original Message-----
From: Michael Gale [mailto:michael.gale () bluesuperman com] Sent: Monday, December 06, 2004 3:26 PM
To: Craig Humphrey; security-basics () securityfocus com
Subject: Re: DMZ / Firewall rule diagramming

Hello,

Check out some firewall appliances ... most of them have some sort of standard.

For example I used the following:

Connections from Internal to the DMZ are allowed if they match one of the forward rules on the firewall.

The forward rules only allow packets from sources addresses to destination addresses on specific ports which are ruled to be a business requirement.

For connections coming from the DMZ to the internal network which are required for business (Example. Postfix SMTP server to forward mail on to Exchange). The DMZ server connects to a proxy or a NATing rule.

DMZ server never know the IP of a internal server, the DMZ network has the same relations with the internal network as the external network does with the DMZ.

So the DMZ mail server would connect it port 25 on the firewall and that traffic would get forwarded to the Exchange server.

That is the standard that I use ... was this what you were looking for ?

Michael


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