Vulnerability Development mailing list archives

Re: Firewall bypassing tool


From: Cynic <cynic () progrock com>
Date: Fri, 1 Nov 2002 17:24:28 -0800 (PST)

Hi,

Please be a little more clear on what it is you are looking for.
There are many simple packet crafting tools, such as hping2 or nemesis, that you can use to create any combinations of 
TCP flags in packets.

Are you trying to find out if your firewall is suffering from a specific vulnerablity to [SYN-FIN] packets?

You can for example use hping2 to create such packets:
hping2 <firewall ip> -S -F -p <blocked port>

And sniff to see if the firewall sends a [SYN-ACK] response or a [RST-ACK]. Most likely it will be a RST since I have 
not heard of any current
firewall vulnerable to such problem, unless it is a very specific one, which was not entirely described in your 
question.

Hope this helps,

Cynic.

--- d_fence <d_fence () gmx net> wrote:
Hi all,=20
I read sometime ago about bypassing the firewall filters which block incomi=
ng=20
(initializing) SYN packets, by sending for example a SYN-FIN packet and=20
establishing that way a connection to a blocked port.. Now  I`m trying to=
=20=20
check wether my firewall would let through such packets, and so I`m searchi=
ng=20
for a tool which would does this.. Do you know any such tools?
--=20

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