IDS: Re: Announcement: Alert Verification for Snort

[Christopher Kruegel <chris () cs ucsb edu>]

> > 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.
christopher


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