Re: Exploit through firewall question

From: Neil (neil@voidfx.net)
Date: Wed Jul 19 2006 - 15:44:32 EDT


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On 7/19/2006 7:03 PM, 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?...
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| 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.
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| 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.
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| What would be the reason to test behind the firewall?
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| Any suggestions?
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| Thanks
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I'm having a little difficulty figuring out which firewall you're
referring to, so I'll try to rationalize each.

If your problem is that your firewall is blocking your exploit, and you
want to do your test from outside the firewall because you feel it will
make you more successful in exploiting the target, then your approach to
management should be simple: In a penetration test, you simulate an
attacker trying to break into the target. If an attacker feels s/he
would be more successful from outside his firewall, then he will move
outside his firewall. For you not to do the same would be a disservice
to your clients, since they are not getting the best simulation of an
attack possible, and they might wind up thinking they're safer than they
are.

On the flip side, if the problem is you want to try exploiting from
inside the client's firewall, you can make an argument for that too
(though a bit weaker). A high percentage of break-ins are inside jobs.
~ That's one reason to have security in depth. So, perhaps you should
try coming in from the outside first, and then from the inside; with the
idea that you're simulating various attack approaches. There's also the
possibility of an attacker walking on site and plugging into the LAN,
which might put him behind the firewall. However, with both of these
arguments to test behind the client's firewall, it depends on the scope
of your penetration test. Perhaps the company trusts its physical
security and employees, and thus doesn't want that sort of test.

You could make a very rational argument for each; however there's a
chance that management simply doesn't care for your argument. In which
case there is nothing to do except advise them of how much this impacts
the quality of the pen-test and do the best you can within your limits.

- -Neil.
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