Re: Announcement: Alert Verification for Snort

From: Martin Roesch (roesch_at_sourcefire.com)
Date: 10/24/03

  • Next message: Martin Roesch: "Re: Announcement: Alert Verification for Snort" 
    Date: Thu, 23 Oct 2003 22:01:26 -0400
To: Christopher Kruegel <chris@cs.ucsb.edu>

    On Oct 23, 2003, at 7:03 PM, Christopher Kruegel wrote:

    >>> In case 2 the "nontextual" isn't a false positive but I think that
    >>> most people are calling it an FP these days. I *personally* think
    >>> that's a misconception. What we have in that case is a *real
    >>> attack* that your IDS is detecting exactly as it was asked to. Just
    >>> because it doesn't have the additional information about the context
    >>> or relevance of the event isn't a problem with the IDS, it's a side
    >>> effect of the way that NIDS have been built for the past 10 years.
    >>
    >> In the not too distant past I would have agreed with this - but I
    >> think as IDS implementations grew, the way people describe FPs has
    >> changed. I think today's IDS *needs* to know "the additional
    >> information about the context and relevance" - because the event you
    >> are referring to is what I'll call an "effective FP". Effective
    >> because any time I spend trying to track down an IIS attack on an
    >> apache box is wasted effort. I completely understand your point
    >> Marty, because an attack did occur, and the IDS did log it. However,
    >> if it is going to log it, then I want it to tell me that the severity
    >> of the attack is lessened because it didn't succeed. Even better, I
    >> want to see the 404 or 403 error, so I can show my boss why I didn't
    >> even bother to look into it.
    >
    > From a theoretical point of view, I think that Marty is right and his
    > classification is correct. In fact, we had a discussion about whether
    > 'alert verification' was the correct term to use. We then concluded
    > that most people don't care why they spent time looking at an alert
    > that doesn't matter to them and that they refer to such alerts in
    > general as false positives. That's why we used the terminology that we
    > did.

    I think alert verification is a fine term, I just want people to
    understand the distinction between false positives and nontextuals. We
    can do something about both of those cases but they require different
    solutions to address. I don't want to confuse the issue if I come out
    with separate solutions that both address "false positives", people
    will ask why I couldn't get it right the first time. :)

         -Marty 

    -- 
Martin Roesch - Founder/CTO, Sourcefire Inc. - (410)290-1616
Sourcefire: Snort-based Enterprise Intrusion Detection Infrastructure
roesch@sourcefire.com - http://www.sourcefire.com
Snort: Open Source Network IDS - http://www.snort.org
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  • Next message: Martin Roesch: "Re: Announcement: Alert Verification for Snort"

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