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Re: Bypassing Firewalls
From: William Hancock <bill.hancock () isthmusgroup com>
Date: Fri, 07 Apr 2006 09:06:41 -0500

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Hi Sparky:

 I don't want to come off sounding to snotty but I need help
considering the facts you're offering us..

1. You say you are pen testing a customer that has 65,000 IPs.
2. Those addresses aren't translated, so a.a.a.a (outside) == a.a.a.a
(inside)
3. You're trying to use nmap as some sort of tunneling tool?
4. You are aware, or at least under the impression, that the only
ingress traffic is HTTP and BIND.
5. You want to use nessus to scan through a firewall to assess open
services and vulnerabilities
6. You've attempted to use the standard old FTP bounce through a
perimeter that only allows 80 and 53.

None of this is really computing that well, 1,2,4, and 6 just don't
make any sense and I'm not even going to begin to explain why.  Nmap
won't help you establish any sort of connection to the inside of the
firewall, and nessus will only scan what it can access.

If you have a client large enough to support that many public IPs and
you're posing questions about quietly slipping ((~ 65535  x 65000) x #
of vulnerabilities nessus will scan for) past a firewall with 2
allowed ports/protocols open on it you're a bit out of your league.  I
would advise you to seek a qualified security consultant to perform
the testing and watch everything he does.  There seems to be some gaps
in your networking knowledge as well and there are lots of great books
out there that could help you, I'm sure someone on list can recommend
a few.

The short answer however, based upon the information you provided, you
need to root a box on the inside, or simply ask permission to use
one,  and stage your attack from there.

Sorry, I'm not yet caffeinated and I need some coffee.

Regards,
Bill Hancock
www.exactconsulting.com

09Sparky () gmail com wrote:
I am a new Pentester and have some general questions as to how to bypass
Firewalls.  I have attempted the standard FTP bounce and fragmentation
attempts in nmap, but have been unsuccessful.  My main question I guess
would be:  How do you get past a firewall, so you could for instance
perform your nessus scanning, etc?  I have a good understanding of all
the steps involved, I just am having problems actually getting them to
work.  Do I need to find exploits in the Firewall, or are there other
more effective ways? 
For instance, I want to do a standard Pen test on a company (class B
network, no NAT).  I have their IP range, but they have a firewall
blocking everything but HTTP and DNS.  How do I get past the firewall to
perform the test on there IP range?

Any help/suggestions would be great,
Thanks,
Sparky

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