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Date:      Fri, 31 Mar 2000 12:14:36 +0100
From:      Brian Somers <brian@Awfulhak.org>
To:        "Brian O'Shea" <boshea@ricochet.net>
Cc:        Joshua Goodall <joshua@roughtrade.net>, Randy Bush <randy@psg.com>, freebsd-net@FreeBSD.ORG, brian@hak.lan.Awfulhak.org
Subject:   Re: Security of NAT "firewall" vs. packet filtering firewall. 
Message-ID:  <200003311114.MAA01613@hak.lan.Awfulhak.org>
In-Reply-To: Message from "Brian O'Shea" <boshea@ricochet.net>  of "Wed, 29 Mar 2000 12:27:15 -0800." <20000329122715.G330@beastie.localdomain> 

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> > However, I think Randy is essentially warning that each private address
> > can be statically mapped to a public one, demonstrating that NAT is not
> > necessarily a security feature, it's a convenience.
> 
> Ok, so that basically answers the question in my last post.  If I
> understand correctly, someone on the same subnet as my router's external
> interface could set a static route to my internal network through my
> router's external interface.  In other words, I am vulnerable to attack
> from anyone who subscribs to the same cable modem service that I do, and
> happens to be on the same subnet (I believe subnets are regional, so
> that means roughly anyone in my neighborhood).  Not to mention anyone
> who manages to compromise one of my neighbor's systems and subsequently
> attack my system.

Hmm, there's a PacketAliasSetTarget() function in libalias that will 
direct all incoming connections to a given IP number irrespective of 
their destination address.  Unfortunately, it's not used by either 
ppp or natd.

I think I'll add a ``nat target'' command to ppp.
-- 
Brian <brian@Awfulhak.org>                        <brian@[uk.]FreeBSD.org>
      <http://www.Awfulhak.org>;                   <brian@[uk.]OpenBSD.org>
Don't _EVER_ lose your sense of humour !




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