[Snort-users] Specific rule for bandwidth

Gabriel Corre gabriel.corre at ...17281...
Tue Sep 15 11:31:00 EDT 2015


To be more precise, is it possible to fire an alert when a certain amount of data is transfered in a specific time interval?

-----Message d'origine-----
De : Gabriel Corre [mailto:gabriel.corre at ...17281...] 
Envoyé : mardi 15 septembre 2015 17:14
À : Davis McPherson (davmcphe) <davmcphe at ...589...>; snort-users at ...8192...sourceforge.net
Objet : Re: [Snort-users] Specific rule for bandwidth

Ok, then it also means I cannot control data transfer in real time with stream_size, right?
Do you know if there is another way?

-----Message d'origine-----
De : Davis McPherson (davmcphe) [mailto:davmcphe at ...589...] Envoyé : mardi 15 septembre 2015 16:47 À : snort-users at lists.sourceforge.net Objet : Re: [Snort-users] Specific rule for bandwidth


The stream size option is evaluated on packets when a rule is evaluated.  The current stream size is computed by subtracting the current 'next seq' from the ISN (or vice-versa to handle wrapping).  The value is computed for the server and client directions and then comparison is done for the directions specified by the rule against the threshold value in the rule using the comparison operator defined by the rule.   There is no reset if the rule is triggered, so the stream size is a count of the number of bytes observed on the stream.

-davis mcpherson


-------- Forwarded Message --------
Subject:        [Snort-users] Specific rule for bandwidth
Date:   Tue, 15 Sep 2015 07:24:11 +0000
From:   Gabriel Corre <gabriel.corre at ...17281...><mailto:gabriel.corre at ...391...7281...>
To:     snort-users at lists.sourceforge.net<mailto:snort-users at ...2987...rge.net> <snort-users at lists.sourceforge.net><mailto:snort-users at ...635...eforge.net>


Hello,

I would like to use "stream_size" as a bandwidth controller. Thus I created this rule to test its functionality:
alert tcp EXTERNAL_NET any -> HOME_NET any (msg:"WARNING! Session bandwidth > 8 bytes"; stream_size:both,>,8"; sid:1000000001;) I would like to know if "stream_size" is reset when the alert is triggered or it still count the number of bytes observed?

The doc says : "The stream size keyword allows a rule to match traffic according to the number of bytes observed, as determined by the TCP sequence numbers." It doesn't pinpoint this aspect and I'm not about my bandwidth test.

Regards,

--

Gabriel Corré
Élève Ingénieur Sécurité & Réseaux, Ops - Core Infrastructure




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