Re: Announcement: Alert Verification for Snort

Hi Raistlin,

On Oct 23, 2003, at 6:35 AM, Raistlin wrote:

>> 1) Detect, Attack Present, Vulnerable: True Positive
>> 2) Detect, Attack Present, Not Vulnerable: Nontextual (i.e. detect
>> requiring contextual data to resolve)
>
> Actually, I think that vulnerable or non-vulnerable is not tied to the
> true/false positive concept... so I'd say:
>
> Detect, Attack Present, Signature Present, [vuln|not]: True Positive

The "signature" (detection method) being present was implicit since
there was a detection. :)

> (thinking of a signature based system, reword it for your favorite
> system)
>
>> 4) No Detect, Attack Present, Vulnerable: False Negative
>> 5) No Detect, Attack Present, Not Vulnerable: ?
>
> Here it is a bit more complex, but I'd say
> No Detect, Attack Present, Signature Present, [Vuln|not vuln]: False
> Negative

I'm leaning that way as well, but I think I'd classify it as somewhere
between a False Negative an a nontextual. Some people might call it a
fortunate happenstance since it reduces the data load from the IDS even
if it is by mistake. :)

> No Detect, Attack Present, Signature Present, Not Vulnerable: a lucky
> false
> negative :)

Exactly!

>> 6) No Detect, No Attack, [vuln|not vuln]: Don't care (true negative?)
>
> True negative is the correct definition, but it encloses also:
>
> No Detect, [Attack|No Attack], No Signature, [vuln|not vuln]

Yes.

>> 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.
>
> I agree wholeheartedly.

      -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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