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Re: Clueless firewall configuration ?
From: "Chris Byrd" <cbyrd01 () gmail com>
Date: Sat, 12 Aug 2006 08:55:42 -0500

A few problems I see with this:

1. Having untrusted traffic on your core switch can cause the
potential for a remote DoS attack against your core.  Switches have
been known to keel over under certain circumstances (the Slammer worm
was one) where there are lots of small packets on the wire.

2. VLAN hopping attacks.  A misconfiguration may make it possible to
inject untrusted traffic onto your trusted network by spoofing VLAN
headers.  A method for bi-directional traffic was recently posted
(sorry, I don't have the ref handy) by using a publically addressable
host.

3. Everyone makes mistakes.  By combining untrusted and trusted
networks on a single switch, the effects of a configuration mistake
could be amplified.

4. Cisco, in my opinion, isn't the best or most secure firewall available.

5. Collapsing the network to that level might make it harder to
monitor and control.  For example, how would you put a network based
IPS between the firewall and the internal segment if you wanted to
impliment one in the future?

Hope this helps,

Chris
www.riosec.com

On 8/11/06, cableguy clueless <cluelesscableguy () gmail com> wrote:
Guys, I need to ask a favor, my boss knows nothing of IT
infrastructure, and our "cableguy" (manages the firewall through a
third party contract) proposed to him an architecture as  follows :

2 cisco 6509 each with firewall blade in them. These function as core
switches for a 1000 users site with lots of vlans and FW roules
between the vlans (oh and we are a big production site that relies on
these cores to let our ciritical bussiness process machines
communicate to the servers).

He wants to create 2 vlans, 1 for untrusted traffic and 1 vlan for DMZ
machines and assign physical ports to these to connect to the
internet. The DMZ vlan would also have some physical ports. These
ports would not be on the core switch but on the access layer switches
that are fiber attached to the distribution switches that attach to
the cores...

Does anyone care to comment on the security issues a setup as this
would pose? would this be pentest bonanza for you guys? and what would
the hackers make of a dmz vlan living in a big switch together with
other vlans?

I have some ideas myself, but would appreciate your take on this. I
know this is the pentest list but it is you guys who get to poke holes
in these designs...

CCG

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