Re: Can Snort do this?

[Erek Adams <erek () snort org>]

On Thu, 16 Oct 2003, Sheahan, Paul wrote:

> I'd like to be able to flag source addresses when they cross a certain
> threshold of connections per minute, hour, or day.
>
> For example, normally if I visit a website and follow normal means to
> purchase a product on that website, then logoff normally, my session
> while on that site might consist of maybe 500 total packets and maybe 50
> of those packets might be TCP SYNs (let's say for example sake). Let's
> say this is normal for a particular site. Now if I get 500 TCP SYNs from
> a same IP address over a certain time period (hours or a day), then I'd
> like to flag this, since this is not normal behaviour.
>
> Can Snort do something like this, like maybe with a TCP SYN preprocessor
> or something? Any tips/recommendations here?

Nope.  Snort's thresholding is signature based.

As for a preproc, it would be the thing to do it, but it's not going to be
an easy thing to do.  Keeping track of SYNs or any other packet for that
amount of time could be a rather memory intensive application.  It's
either that or make it really slow and go to disk...

Cheers!

-----
Erek Adams

   "When things get weird, the weird turn pro."   H.S. Thompson


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