full-disclosure - NAT router inbound network traffic subversion

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From: bart2k at hushmail.com (bart2k@...hmail.com)
Subject: NAT router inbound network traffic subversion

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Check it here -> http://www1.cs.columbia.edu/~smb/papers/fnat.pdf

This should help clarify why NAT can not be considered a security
feature.


On Thu, 27 Jan 2005 22:12:19 -0800 Kristian Hermansen
<khermansen@...technology.com> wrote:
>I have Googled around and asked a highly-respected Professor at my
>University whether it is possible to direct packets behind a NAT
>router
>without the internal 192.168.x.x clients first requesting a
>connection
>to the specific host outside.  The answer I received is "not
>possible".
>I also asked if this can be thought of as a security feature, to
>which
>the reply was again "yes".
>
>Now, I wouldn't place all my bets on his answer and I am calling
>on
>someone out there to clear up my question.  If NAT really does
>only
>allow inbound connections with a preliminary request as he
>suggests, it
>seems that the only way to get an "unauthorized" packet behind the
>router is by some flaw in the firmware of the device.
>
>How about if the client has requested a connection to Google.com
>from
>behind his Linksys home NAT router: would it be possible for an
>outside
>attacker to spoof packets from Google's IP to get packets into the
>network?  Or do we need to know the sequence numbers as well?  Or
>is
>there an even more devious way to get packets on the inside
>without a
>client's initiative?
>
>Has there been any research into this?  Are there statistics on
>worm
>propagation and exploited network hosts in relation to those
>individuals
>that did not own routers (and instead connected directly to their
>modem)?  If *all* home users on the Internet had NAT routers
>during the
>summer of 2003, would we have significantly slowed the spread of
>Blaster?  I believe these all to be very important questions and
>the
>security aspects of the ability to route packets behind NAT really
>interests me...maybe some of you can elaborate :-)
>--
>Kristian Hermansen <khermansen@...technology.com>
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