Re: signature true positive or not

[Joel Esler <jesler () sourcefire com>]

The VRT can tell you if the alert that you receive matches the research
that we have done about the vulnerability.

If the rule alerts.

J

On Tue, Jan 24, 2012 at 10:50 AM, JJC <cummingsj () gmail com> wrote:

> Beyond that, as was mentioned earlier, we cannot possibly tell you if it
> was a true positive or a false positive in your environment.  Often even if
> you provide a PCAP.  Sure, with a PCAP we could probably say.. this was a
> legitimate attack, but if the target system is not vulnerable....  There
> are a number of factors that YOU as the analyst must be able to answer and
> work your way through to determine this.
>
> JJC
>
>
> On Tue, Jan 24, 2012 at 6:31 AM, Kevin Ross <kevross33 () googlemail com>wrote:
>
> > Oh right. Well it is just that when VRT release their rulesets they will
> > tell you whether or not by default it is enabled or disabled. If it is a
> > rule you would like to run you have to enable it yourself (using
> > pulledpork) and vice versa for disabling any enabled by default rules you
> > don't need. In contrast the emergingthreats.net rules are largely
> > distributed entirely enabled unless it is a performance/false positive
> > concern and it is up to you to disable them as needed.
> >
> > Kind Regards,
> > Kevin Ross
> >
> > On 24 January 2012 09:50, Yossi <yasayag () gmail com> wrote:
> >
> > >  I just wanted to understand the meaning of "Default rule state" =
> > > DISABLED.
> > > Should I disabled the rule from the rule files, or the rule hasn't been
> > > updated.
> > >
> > > yossi
> > >
> > >
> > > On 01/24/2012 11:33 AM, Kevin Ross wrote:
> > >
> > > I am not sure exactly what you mean but I will make a few guesses and
> > > hope I answer your question:
> > >
> > > 1) If you mean about it saying it is disabled in the rule update that
> > > means by default it is disabled and it is up to you whether or not you want
> > > to enable it.
> > > 2) If you did enable it and you got a hit we won't be able to determine
> > > if it was a true positive (when it really is an attack) or a false negative
> > > (when the sig fires but the traffic isn't an attack) unless you provide a
> > > packet.
> > >
> > > Kind Regards,
> > > Kevin Ross
> > >
> > >
> > > On 24 January 2012 09:11, Yossi <yasayag () gmail com> wrote:
> > >
> > > >  Can someone explain the meaning of the the content which I'd found on
> > > > the VRT site  .
> > > >
> > > >  Sourcefire VRT Rules Update
> > > > Date: 2011-12-28
> > > >
> > > > This is the complete list of rules modified and added in the Sourcefire
> > > > VRT Certified rule pack for Snort version 2.9.1.0.
> > > >
> > > > The format of the file is:
> > > >
> > > > *gid:sid <-> Default rule state <-> Message (rule group)*
> > > > New Rules:
> > > >
> > > >  * 1:20821 <-> DISABLED <-> EXPLOIT Apache APR header memory corruption attempt (exploit.rules)
> > > >
> > > >
> > > >
> > > >  Is the signature 20821 (EXPLOIT Apache APR header memory corruption
> > > > attempt) true positive and should be disabled or not?
> > > >
> > > > Thanks
> > > >
> > > >
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-- 
Joel Esler | http://blog.snort.org | http://vrt-blog.snort.org |
http://blog.clamav.net
Twitter:  http://twitter.com/snort

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