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Re: TCP Sack processing

from [Joachim Schipper] Network Security [Permanent Link]
Subject: Re: TCP Sack processing
Date: Thu, 11 Aug 2005 10:34:43 +0200 
On Tue, Aug 09, 2005 at 04:28:10PM -0400, snort user wrote:

Greetings.

Does TCP stream reassembly algorithm need TCP SACK processing for 
completeness ?
Are there scenarios that an IDS/IPS would miss an attack if it does
not take the selective acks into consideration.

Any comments/opinions/pointers is appreciated.

Thanks


Well, I am not an expert, but...

Suppose I have an exploit that requires a TCP connection. I open the
connection, send packet #1 and #3, and then sent #2 after #3 has been
SACK'ed. Wouldn't that work, and bypass your IDS, especially if the
exploit is divided over the packets in a smart way?

                Joachim

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