[Snort-users] T/TCP resources -- answer for Andy Wood

MH procana at ...4296...
Fri May 2 03:20:39 EDT 2003


Hi Andy,

Richard is right on the money with his explanation and references.
There is a difference to what I explained in my post on truncated tcp 
options and T/TCP detected.
To understand T/TCP you must look to the ultimate source (RFCs 1379 and 
1644) :)

Hope this helps,
Mike



At 09:28 PM 5/1/2003 -0400, Andy Wood wrote:
>         You may also reference this msg, sent 4/27/2003 @ 5am, for an
>explanation:
>
>http://sourceforge.net/mailarchive/message.php?msg_id=4437405
>
>
>-----Original Message-----
>From: Richard Bejtlich [mailto:richard_bejtlich at ...131...]
>Sent: Thursday, May 01, 2003 6:31 PM
>To: snort-users at lists.sourceforge.net
>
>Hello,
>
>Lots of people have mentioned how to disable T/TCP in Snort, but no one
>mentioned what it is -- so far as my search of the list archives goes.  :)
>
>T/TCP recognizes that many sessions are
>request-response, like HTTP, so T/TCP tries to minimize overhead.  For
>example, the client sends a SYN/request/FIN in one packet.  The server sends
>its SYN/ACK/response/FIN, and the session concludes with the client ACKing
>the server's FIN.
>
>For those who want more than my simplistic rendition of the protocol, see
>RFC 1379 (http://www.faqs.org/rfcs/rfc1379.html).
>
>Other resources include:
>
>T/TCP home page:
>
>http://www.kohala.com/start/ttcp.html
>
>1998 Phrack Article by Route:
>
>http://www.phrack.com/show.php?p=53&a=6
>
>As for why you're seeing so much traffic which matches Snort's T/TCP
>checking code, I'd have to see some raw captures to analyzing what's
>happening.
>
>Sincerely,
>
>Richard Bejtlich
>richard at taosecurity dot com
>http://taosecurity.com
>
>
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