Re: Snort with an expert system

[Richard Bejtlich <taosecurity () gmail com>]

On Thu, Jun 25, 2009 at 2:55 PM, Greg Shipley<gshipley () neohapsis com> wrote:
> I respect the spirited and intelligent conversation here, but at the
> risk of sounding like a) an old guy that's been following this stuff
> for too long and b) a complete jerk:
>
> 1. IDS vendor / IDS software engineer / uber-geek view: "it's not
>   technically a false-positive because if signature/ rule /
>   pattern-match/ neugent/ whatever fired on x and it was programmed
>   to identify q but you have to factor in y, and z, and..."
>
>   <bang head here -----> X
>
> 2. Infosec operational person trying to do his job: "Was I attacked
>   and was the attack successful?  Yes or NO will suffice, thank you."
>
> I submit that for the vast majority of consumers of IDS technology we
> really only give a crap about #2.  So if the device can give us a
> reasonably accurate answers to #2 we are happy.  And if it can't we
> are unhappy.
>
> I think the fact we've been discussing these topics for close to
> twenty years now suggests that we aren't happy, but maybe I'm too old
> and being a jerk.  :)
>
> My .01,
>
> -Greg

Hi everyone,

This is a cool debate.  I submit that it is technically impossible to
build anything that will not 100% avoid "#2" false positives.  I'm a
#1 guy myself; the only real "false positive" is the system telling
you it saw something, when that something actually never happened,
e.g., "IDS: I saw ICMP!  User: There was no ICMP; your engine isn't
working properly."

For any case you develop that you think is absolutely, positively,
without a doubt an "intrusion" that you could identify with an IDS, I
can probably develop a case where that activity could turn out to be
legitimate, and therefore, in the eyes of the organization, a "false
positive."

I think the "IDS" has been misnamed from the beginning.  (Blame Mr.
Anderson?)  It should have been Attack Indication System or something
similar.  After all "If you can detect it, why can't you prevent it?"
Now it's really time to "bang head here."  :)

Sincerely,

Richard

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