Snort IDS + TAPS

[Eric Hines <eric.hines () appliedwatch com>]

All:

We are deploying Snort on a two interface appliance, connected to a GigE 
Netoptics Ethernet TAP. By design, TAPs are split up into (2) monitoring ports, 
(RX split up between two ports):

INTERFACE 1 - (from router -> switch) [ ] 
INTERFACE 2 - (from switch -> router) [ ]

Obviously because the RX is split up between 2 ports, if we bind Snort to 
interface 1, it will only see traffic from ROUTER -> SWITCH. If we bind Snort 
to inteerface 2, it will only see traffic from SWITCH -> ROUTER. Therefore, we 
must bind Snort to both interfaces to see both sides of the session. Here's 
where the problem is. If 2 separate Snort processes are monitoring two 
interfaces, how is the Snort on each interface going to maintain state for all 
the connections? Each snort process only sees 1/2 of the connection! 

I've spoken to someone that has said Snort requires modification to listen on a 
tapped device because of this very issue. Someone please advise.


-------------------------------------------
Eric Hines
CEO, Chairman
Applied Watch Technologies, Inc.
web: http://www.appliedwatch.com
email: eric.hines () appliedwatch com
-------------------------------------------
Direct: (877) 262-7593 x327 - Toll Free
Fax: (877) 262-7593 
Main: (877) 262-7593 (9am-5pm CST)
-------------------------------------------
"Break free of the IDS Web Browser Prison at
Applied Watch Technologies"





---------------------------------------------------------------------------
Network with over 10,000 of the brightest minds in information security
at the largest, most highly-anticipated industry event of the year.
Don't miss RSA Conference 2004! Choose from over 200 class sessions and
see demos from more than 250 industry vendors. If your job touches
security, you need to be here. Learn more or register at
http://www.securityfocus.com/sponsor/RSA_focus-ids_031023 
and use priority code SF4.
---------------------------------------------------------------------------