RE: on NIDS/NIPS tuning

["Hazel, Scott A." <Scott.Hazel () unisys com>]

This is a fundamental question we've been dealing with as well. By
default we tune the IDS. But when the SIM tool is thrown into the mix,
the question becomes where to tune. Theoretically, the SIM uses all the
data it sees to correlate attacks, attackers, trends in suspicious
activity, etc. If you tune what appears to be noise at the IDS, you
could potentially be tuning out data the SIM uses to correlate and alert
on a higher quality event. 

Conversely, tuning out known FP's at the IDS should create a higher
quality data stream for the SIM to use. Logic points me to opening the
IDS and letting the SIM do the work. The SIM would also be where the
data was tuned. In the end, it seems you could go either way depending
on how you want your alerts served up to you and how much disk you've
got to hold all that data in the IDS. 

Thanks for starting this thread though. Tuning an IDS seems as much an
art as a science. I'm glad to see input on how the rest of you handle
it. 

Scott Hazel

-----Original Message-----
From: Gary Halleen [mailto:ghalleen () cisco com] 
Sent: Friday, June 10, 2005 4:17 PM
To: 'Drew Simonis'; 'Anton A. Chuvakin'; focus-ids () securityfocus com
Subject: RE: on NIDS/NIPS tuning

I'm seeing many organizations now tuning not on the IDS, but on the SIM
product they're using for monitoring them.

Gary
 

-----Original Message-----
From: Drew Simonis [mailto:simonis () myself com] 
Sent: Friday, June 10, 2005 6:02 AM
To: Anton A. Chuvakin; focus-ids () securityfocus com
Subject: Re: on NIDS/NIPS tuning

> All,
>
> I was thinking about some issues with IDS alerts (their volume, etc) 
> and realized I could use some help from the list. It might also be a  
> fun discussion item.
>
> So, here it is: how many folks who buy/download a NIDS/NIPS actually 
> tune it? Long time ago when I was asking this question the previous 
> time, I was scared to learn that lots of people do not tune their 
> NIDSs. Is it any better now?

I know that, in my experience, many orgs don't tune at all.  The fear is
that they might do it wrong and thereby miss some important event.  IMO,
this is a stupid way of thinking, but I bet it isn't as rare as it
should
be.  

In other cases, people do not tune and rely on a correlation engine or
MSS
to filter the events.  This is better, but really just moves the tuning
to a
different level.

Personally, I tune sigs and also tailor the sig sets to the devices
being
monitored.  For example, if there are no webservers on a segment, I
might
not be as inclined to use sigs that check for Apache exploits.  I've
never
really measured the impact on the system vs. the administrative cost of
doing this, however, so it is quite possible I am wasting time for a
negligable benefit.  

On the tuning side, I believe that filters and exclusions should be part
of
the incident response lifecycle.  If I am alerted to an event by an IDS,
I
investigate and discover that the event was benign or did not take
place, a
filter should result, and thus be properly documented.  

-Ds

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