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Date:      Wed, 28 Nov 2001 22:00:46 +0200
From:      Giorgos Keramidas <charon@labs.gr>
To:        Allen Landsidel <all@biosys.net>
Cc:        freebsd-security@FreeBSD.ORG
Subject:   Re: Best security topology for FreeBSD
Message-ID:  <20011128200045.GB8893@hades.hell.gr>
In-Reply-To: <5.1.0.14.0.20011126175234.00aeb5e8@rfnj.org>
References:  <200111231250.fANCoha19105@cwsys.cwsent.com> <20011122031739.A226@gohan.cjclark.org> <200111231250.fANCoha19105@cwsys.cwsent.com> <5.1.0.14.0.20011126175234.00aeb5e8@rfnj.org>

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On 2001-11-26 18:07:21, Allen Landsidel wrote:
>
> >Defense in depth. Examples: A glitch/security breach in Firewall1's
> >ruleset/software does not necesarily expose the internal network.
> >Any vulnerabilities in Firewall2 are harder to exploit when protected
> >by Firewall1.
>
> I have to say.. I've been biting my tongue on this topic, but I feel like
> speaking up now.
>
> The above paragraph is well and good for actual firewalls (like you find in
> vehicles) and actual DMZ's (like you find in a warzone) because depth means
> that many more layers of opposing force you have to fight your way through.
>
> It seems pretty meaningless however when applied to a network.(*)
>
> Chances are if an attacker can compromise "Firewall1" then they can use an
> identical exploit/hole/vulnerability to exploit "Firewall2."  In war, there
> are such exploits, and they're called bullets.

That is why most books I've read on firewalls suggest the use of
`different' types of firewalls when one is stacked behind the other.
To avoid having two identical firewalls that can be passed with
exactly the same bugs/exploits :-)

The depth principle still applies, IMHO.

-giorgos

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