[Snort-users] NEWBIE: rule writing walkthru?

Keith W. McCammon mccammon at ...11827...
Tue Jul 13 07:12:03 EDT 2004

>     I'm brand new to Snort.  Know what it is capable of and want to play
> with it but I'm having trouble getting out of the blocks.  I'm reading
> through the docs and it seems pretty straight forward but I would like
> to find a walkthru/tutorial or something like that for rule writing.

The documentation is a pretty good place to start.  It's pretty
standard stuff.  If some condition exists, generate an alert or log
(or don't).  Start there, and work your way through things like the
TCP flags, flows, and thresholding, which will reduce the noise
generated by your more generic rules.
>     I'm wanting to use Snort as both an IDS AND a web usage monitor.
> I'm working with a state agency and money is...well...there is no money
> to spend on a Netappliance machine or something of that ilk.  I was
> thinking that if Snort can detect intrusions it must also be able to do
> the web usage thing given the correct rule.

In theory, you could use it to monitor web traffic.  You could start
it in sniffer mode, with name resolution (al la tcpdump) and catch web
traffic that way.  Goes without saying that you'll need to use another
tool to analyze the data, as you'll get a lot more than you probably
want, if you just want to see who's going where and when.

Alternatively, you could set up one of the open-source proxy systems,
which is actually supposed to be used for something along these lines.
 This would preclude you from trying to tweak Snort into giving you
something that it isn't "intended" to do (in quotes because, in
theory, you can do damn near anything with it, provided that you
understand what you're after very specifically).

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