Massive stupidity (Was: Re: TCP vulnerability)

Mike Tancsa mike at sentex.net
Wed Apr 21 01:23:46 UTC 2004


At 05:09 PM 20/04/2004, Richard A Steenbergen wrote:

>party to know which side won the collision handling. Therefore you need
>262144 packets * 3976 ephemeral ports (assuming both sides are jnpr, again
>worst case) * 2 (to figure out who was the connecter and who was the
>accepter) = 2084569088 packets to exhaustively search all space on this
>one single Juniper to Juniper session. Now, lets just for the sake of
>argument say that the router is capable of actively processing 10,000
>packets/sec of rst (a fairly exagerated number) and still have this be
>considered a tcp attack instead of a straight DoS against the routing
>engine. This will still take 208456 seconds, or 57.9 hours.
<snip>
I dont understand why the large differences in claims

http://www.ietf.org/internet-drafts/draft-ietf-tcpm-tcpsecure-00.txt

says
    Modern operating
    systems normally default the RCV.WND to about 32,768 bytes. This
    means that a blind attacker need only guess 65,535 RST segments
    (2^^32/(RCV.WND*2)) in order to reset a connection. At DSL speeds
    this means that most connections (assuming the attacker can
    accurately guess both ports) can be reset in under 200 seconds
    (usually far less). With the rise of broadband availability and
    increasing available bandwidth, many Operating Systems have raised
    their default RCV.WND to as much as 64k, thus making these attacks
    even easier.


Also, with the various 'bots' at peoples disposal, why the assumption the 
attack would not be distributed.

         ---Mike 




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