Re: CVE selection for IDS/IPS signature rules

[Enigma <enigma () security-fu com>]

Leon Ward wrote:
> A quick comment on the below point:
>
> > 2. Keep in mind that CVE is Common **Vulnerability* *and Exposures,
> >     so it covers any vulnerability where IDS/IPS are generally
> >     exploit-centric.  How are you going to detect if a vulnerability
> >     is exploited if there is no publicly known exploit?  How do you
> >     find something when you don't know what it looks like?
>
> All leading IPS venders provide (or at least claim to provide) a 
> vulnerability based detection capability.
> The *idea* behind this is simple. Model the protocol and all the 
> required triggering conditions for the vulnerability to be exploited, 
> and it doesn't matter what exploit-code is being used.
>
> <Disclaimer : I work for Sourcefire>
>
> Snort has had this capability for years. For those interested a VRT 
> (Sourcefire's Vulnerability Research Team) white paper is available 
> that details this process with examples.
>
> -Leon
>
>
> On 3 Jun 2008, at 18:43, Enigma wrote:
>
> > Ravi Chunduru wrote:
> > > Hi,
> > >
> > > There are over 30000 CVE vulnerability reports.  Many IDS/IPS devices
> > > have around 4000-5000 signature rules. My guess is that these
> > > signatures may cover (detect)around 4000-7000 attacks.  23000 to 26000
> > > CVEs, that is, significant number of CVEs are not covered by IDS/IPS
> > > devices.
> > >
> > > I am guessing that there is reason for this. IDS/IPS vendors may be
> > > selecting few CVEs for developing signatures. What is the selection
> > > criteria followed in industry? One criteria, I know is that Network
> > > IDS/IPS devices don't need to worry about attacks that can only be
> > > mounted on the local machine, that is,  NIDS/NIPS devices only need to
> > > worry about detection of attacks mounted remotely. Are there any other
> > > considerations?
> > >
> > > Thanks
> > > Ravi
> > >
> > > ------------------------------------------------------------------------ 
> > >
> > > Test Your IDS
> > >
> > > Is your IDS deployed correctly?
> > > Find out quickly and easily by testing it with real-world attacks 
> > > from CORE IMPACT.
> > > Go to 
> > > http://www.coresecurity.com/index.php5?module=Form&action=impact&campaign=intro_sfw to 
> > > learn more.
> > > ------------------------------------------------------------------------ 
> > Couple of things:
> >
> >  1. If you are talking about Network IDS/IPS, not all vulnerabilities
> >     are remotely exploitable.  Some local vulnerabilities can only 
> > be      detected by a HIDS if they can be detected at all.
> >  2. Keep in mind that CVE is Common **Vulnerability* *and Exposures,
> >     so it covers any vulnerability where IDS/IPS are generally
> >     exploit-centric.  How are you going to detect if a vulnerability
> >     is exploited if there is no publicly known exploit?  How do you
> >     find something when you don't know what it looks like?
> >
> >
> > ------------------------------------------------------------------------
> > Test Your IDS
> >
> > Is your IDS deployed correctly?
> > Find out quickly and easily by testing it with real-world attacks 
> > from CORE IMPACT.
> > Go to 
> > http://www.coresecurity.com/index.php5?module=Form&action=impact&campaign=intro_sfw to 
> > learn more.
> > ------------------------------------------------------------------------
This is a little off topic.  Not knocking Sourcefire or VRT (3D is great 
and I use the VRT sigs all the time) but I have found these type of 
signatures to have the highest rate of false positives.  Don't get me 
wrong, these are useful when there isn't anything else but signatures 
developed from public or at least seen-in-the-wild exploits are much 
more accurate.

------------------------------------------------------------------------
Test Your IDS

Is your IDS deployed correctly?
Find out quickly and easily by testing it 
with real-world attacks from CORE IMPACT.
Go to http://www.coresecurity.com/index.php5?module=Form&action=impact&campaign=intro_sfw 
to learn more.
------------------------------------------------------------------------