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

Andy Wood andy.wood at ...9040...
Thu May 1 18:33:53 EDT 2003


	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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