RE: Clueless firewall configuration ?

["Smith, Michael J." <Michael.J.Smith () unisys com>]

My networking guys try to do this stuff all the time--what happens when
you have too many Cisco-certified people in one room at the same time.
Do a google search for "vlan hopping" and decide for yourself it that is
enough of a risk.  I think the biggest problem is that it is way too
easy to misconfigure any piece of this setup.  The important thing to
say is that instead of a defense-in-depth, you're now looking at a
single device being the keystone of your security.

Since I deal with this scenario all the time, I hit upon a somewhat
compromise.  I enforce hardware segregation for external/Internet-facing
vlans, but I'm OK with all the DMZ vlans being on the same switch, and
all the internal DMZs on another switch.  Depending on the criticality
of the system and how much I trust the admins, I might be convinced to
do DMZ and internal together, but it's on a case-by-case basis.

HTH
--Mike



Michael J Smith, CISSP-ISSEP michael.j.smith () unisys com
Information Security Architect
703.579.2552 O
703.855.0890 C
"Those who do not understand Unix are condemned to reinvent it, poorly."
--Henry Spencer 

 

> -----Original Message-----
> From: Ng, Kenneth (US) [mailto:kenng () kpmg com] 
> Sent: Monday, August 14, 2006 1:41 AM
> To: cableguy clueless; pen-test () securityfocus com
> Subject: RE: Clueless firewall configuration ?
>
> This is very difficult to set up completely correctly.  And 
> your always open to the possibility of an unpublished exploit 
> being able to get around your rules.  And while I do not know 
> if it is still possible, I remember someone demonstrating 
> injecting packets from one vlan to another a few years ago.  
> And as the infrastructure changes, you have to make double 
> sure that you are entirely correct.  Conversely, if you use 
> physically separate hardware, it's a lot easier to get it right, or
> close enough to right that it doesn't matter much.   
>
> -----Original Message-----
> From: cableguy clueless [mailto:cluelesscableguy () gmail com]
> Sent: Friday, August 11, 2006 4:08 PM
> To: pen-test () securityfocus com
> Subject: Clueless firewall configuration ?
>
> 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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