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Re: IP Session Hijacking And Spoofing
From: "simsjs" <sims () interex org>
Date: Fri, 22 Nov 2002 09:23:28 -0800

With IP Spoofing there is no need to guess the sequence number since there is no session currently open with that IP 
address. The way that the traffic would get back to you is by using source routing. This is where you tell the network 
how to route the output and input from a session, then you simply sniff it from the network as it passes by you. But 
you have to make sure you put in a route that will both reach its destination and pass through your own network.

As far as guessing the sequence numbering for session high-jacking, I really have no idea, but there are programs that 
will attempt to guess these for you. The one I am thinking of (whose name escapes me at the time) will allow you to 
watch a session, reset a session, or hijack it.

Hope some of this helps.


*********** REPLY SEPARATOR  ***********

On 11/19/2002 at 11:33 AM LEHMANN, TODD wrote:

I have read some documentation on IP Spoofing, and from what I have read,
sounds like you must determine the sequence number of the host before you
can spoof. However, I don't understand why you would have to determine the
sequence if you are creating a new session with the host under a false IP.
Wouldn't the creation of the new TCP session negotiate the sequence number
at that time?

I also failed to understand how the traffic gets back to you if you are
telling it to respond to another host. Can someone shine some light on this
for me?

When it comes to session high-jacking, how does one go about determining
sequence number on a host that uses a random number seed to create the
sequence? Is it some form of complex algorithms or is it just impossible
unless you create the session?

Todd Lehmann
Systems Analyst I
VPN Subject Matter Expert

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