Re: Clueless firewall configuration ?

["Chris Byrd" <cbyrd01 () gmail com>]

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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This List Sponsored by: Cenzic

Concerned about Web Application Security? 
Why not go with the #1 solution - Cenzic, the only one to win the Analyst's 
Choice Award from eWeek. As attacks through web applications continue to rise, 
you need to proactively protect your applications from hackers. Cenzic has the 
most comprehensive solutions to meet your application security penetration 
testing and vulnerability management needs. You have an option to go with a 
managed service (Cenzic ClickToSecure) or an enterprise software 
(Cenzic Hailstorm). Download FREE whitepaper on how a managed service can 
help you: http://www.cenzic.com/news_events/wpappsec.php 
And, now for a limited time we can do a FREE audit for you to confirm your 
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