Snort mailing list archives

Re: Can I do the flow equiv of "Flags:S"?


From: Matt Kettler <mkettler () evi-inc com>
Date: Tue, 20 May 2003 14:49:07 -0400

At 11:34 AM 5/20/2003 +1200, Jason Haar wrote:
Hi there

I'm wanting to capture outgoing TCP connections irrespective of whether or
not a front-end firewall is blocking that port. I know "Flags:S" does that
trick - but then tcp reassembly doesn't occur.

Is there a way of using the "flow:" option to do this?

[i.e. flow:established doesn't work in the case a firewall stops the 3-way
TCP handshake from finishing]

I guess my question is why would you want to use flow for this?

flow is _intended_ for stateful analysis.. By invoking flow: instead of flags: you're specifically stating that you're only interested in connections which have negotiated themselves to a particular state.

If you want stateless analysis flags _is_ really the option you want to use.

Flow isn't an absolute replacement for flags.. it's just for some situations it works better, others it doesn't.. pick the right one for the right job and you'll be happy.




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