Security Basics mailing list archives

Re: IP Spoofing/Masquarading


From: "M.D.Mufambisi" <mufambisi () gmail com>
Date: Wed, 9 Sep 2009 11:26:37 +0200

Marco,

Thank you very much for the clarity. I had confused things. Source
field is not used for routing. I had missed that. Thanks.

On 9/9/09, Marco Ivaldi <raptor () mediaservice net> wrote:
On Wed, 9 Sep 2009, M.D.Mufambisi wrote:

I understand that IP packets can be spoofed ie change the source
address to make it look like they originated from the internal LAN.
However, when this is done across the internet, with a private IP
address in its source field, how does this packet get routed through
the internet?

The source field is not relevant to IP routing, only the destination is. I
strongly suggest you to read "TCP/IP Illustrated Vol. 1" by W. Richard
Stevens [1].

On the other hand, if proper egress filtering [2] is in place, you'll have
trouble spoofing the source address of the packets leaving your network.

[1].
http://books.google.com/books?id=-btNds68w84C&lpg=PA37&ots=e-u0USRsms&dq=ip%20routing%20stevens&pg=PA37#v=onepage&q=&f=false
[2]. http://en.wikipedia.org/wiki/Egress_filtering

Hope this helps,

--
Marco Ivaldi
Lead Security Analyst     Data Security Division
@ Mediaservice.net Srl    http://mediaservice.net/



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