Re: Exploit through firewall question

[Allen Pomeroy <apomeroy () networkforensics ca>]

mr.nasty () ix netcom com wrote:
> Thanks for the responses. You've confirmed what I had passed to mgmt. But I still have a problem (with mgmt) 
> understanding why?...
>
> I perform vulnerability analysis on our outside (public) web presense, usually during development and then after it's 
> been deployed. I basically use the same tools for each.
>
> Mgmt wants me to only test through the firewall as if I'm coming in like the public. The rational is that the fw will 
> prevent any attacks though ports other than 80 and 443. Therefore, there is no reason to change this configuration.
>
> What would be the reason to test behind the firewall?
>   
Performing a VA from the outside could be considered a valid point, but 
testing behind the firewall - not restricting your testing to 80/443 - 
then allows you to present a listing of the the next logical threats 
that exist.  Tools like core impact follow this logic of exploiting an 
external point of presence then tunneling or burrowing through to the 
next concentric network access rings potentially performing network 
scanning of all ports from the compromised point to other internal 
nodes.  You need to know what threats exist should that external point 
of presence be compromised.

In architectures that I recommend, this point illustrates the need for 
defense in depth.  eg. establish smaller, logical DMZ zones, and within 
those various DMZ zones, ensure that only the communication that is 
necessary is enabled.  Too many times I've seen single layer defense 
architectures fail - the crunchy on the outside and soft in the middle 
concept.

HTH

AP
--
Allen Pomeroy
www.networkforensics.ca


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