[Snort-users] Alerting in near-real-time

Martin Roesch roesch at ...1935...
Thu May 10 11:31:26 EDT 2007

Hash: SHA1

Snort has two output facilities, alerting and logging.  It sounds  
like you've got the logging facility pretty much figured out but you  
haven't quite gotten the alerting part yet.

When you start up a Snort instance, you can setup both the logging  
output option (like unified) as well as the alerting output option.   
Generally if you want real-time alerts you can either setup unified  
alerting to go with unified logging and have a second instance of  
Barnyard running to process the alert data and inform you via your  
selected method or you can go direct to one of the other alerting  
output facilities.

The easy answer is to send alerts someplace like syslog and use a  
syslog monitor like swatch to inform you via email when an even that  
you're interested has happened.  That way you can be pretty specific  
about what kinds of alerts you get informed about immediately and  
which ones are lower priority (i.e. in the database).

Another option is to use a monitor like sguil that'll give you a real- 
time view into the database, but that's a little more complicated to  
get setup while at the same time being a lot more useful than syslog...


On May 10, 2007, at 10:24 AM, David.Ryan at ...13912... wrote:

> Thanks to all on the list for their help to date.
> I am still trying to get my head around something which I still  
> can't understand in the overall snort model and I'm hoping someone  
> can set me straight on what I'm missing (or what I'm assuming  
> incorrectly).  I may have asked this to the list before, but I  
> can't find it.  Apologies if I'm asking the same question again.
> What I have got so far . . .  snort sniffs packets, matches those  
> packets against rules and can log the results via a variety of  
> output plugins to various repositories.  It can log directly to a  
> variety of databases, but from an optimisation point of view it is  
> better to use unified output, pass that to something like barnyard  
> and have *it* log to the database.  Net result is that events are  
> logged in the database.  This appears to be the end of snorts  
> involvement in the process from what I can see.
> With the data now in the database something else needs to process  
> it further if any value is to come out of the data.  There are  
> various apps such as BASE, snortnotify, snortsnarf, etc .. . .  
> which will either summarise the data and mail it out or else  
> present it via a webpage for analysis.  The problem I'm thinking of  
> is that this is fine for trending or where there is someone looking  
> at the data to review recent traffic, but I don't see how this can  
> provide any sort of near-real-time alerting.
> Say for example I am happy to look through reports every morning at  
> 0900 to see what happened yesterday, but I *really* *really* want  
> to get an SNMP or SMTP alert when rule # 3423 is triggered or the  
> string "bad stuff" is spotted.  What do people use for this type of  
> scenario ?  I understand that it would probably involve running a  
> query against the database every X minutes and acting on the  
> results of the query, but I can't understand how there aren't a set  
> of apps out there (or at least ones I can find) that do this type  
> of thing as I would have thought it was a common requirement.
> David
> =================================
> David Ryan
> IT Security Engineer, Global IT Security
> Quintiles, Global IT - Infrastructure, QDUB
> david.ryan at ...14057...
> v:  +353-1-819-5186, GMT+0
> m: +353-87-124-9108
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- --
Martin Roesch - Founder/CTO, Sourcefire Inc. - +1-410-290-1616
Sourcefire - Security for the Real World - http://www.sourcefire.com
Snort: Open Source IDP - http://www.snort.org

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