Re: Question regarding a rule

[James Lay <jlay () slave-tothe-box net>]

On 2014-06-24 12:00, Charlie Egan wrote:
> Cheers for both of your replies. I tried adding the to_server bit
> funnily enough just before you wrote that email, still no luck
> unfortunately.
>
> Ive tried adding the detection filter on as well, still no luck with
> that either! The alerts are still piling through a few minutes after,
> over the period of about three seconds. As well as the time delay, Im
> confused as to why there are so many alerts. Apologies, didnt mean to
> email you back directly James.
>
> Cheers
>
> On Tue, Jun 24, 2014 at 6:39 PM, James Lay <jlay () slave-tothe-box net
> [12]> wrote:
>
> > On 2014-06-24 11:26, Y M wrote:
> > > Ok, GUI is out of the way.
> > >
> > > I am just guessing here, but since there is no flow direction in
> > the
> > > rule; only "established" without a flow direction (to_server,
> > > from_client, etc...) Snort will alert after it flushes the tcp
> > > sessions, I am almost sure that I read this somewhere. If you
> > use,
> > > for
> > > example, to_server, Snort would alert as soon as the content
> > matches
> > > and knows that it was you (the client) who established/initiated
> > the
> > > connection (through stream5) and alert based on that. However, I
> > > stand
> > > corrected on all of the above.
> > >
> > > If you add the flow direction to your rule, does that change the
> > > alerting behavior?
> > >
> > > -------------------------
> >
> > > Date: Tue, 24 Jun 2014 18:09:05 +0100
> > > Subject: Re: [Snort-sigs] Question regarding a rule
> > > From: chas5873 () gmail com [1]
> > > To: snort () outlook com [2]
> > > CC: snort-sigs () lists sourceforge net [3]
> > >
> > > Cheers for the reply mate.
> > >
> > > Im not using a GUI, just running it in through a terminal. Its
> > the
> > > only rule which its happening with so far, confusing me to say
> > the
> > > least!
> >
> > > On Tue, Jun 24, 2014 at 6:06 PM, Y M <snort () outlook com [4] [8]>
> > wrote:
> > > > Are you using a GUI or just running in console mode to view the
> > > > alerts? "Usually", in a GUI scenario, alerts are cached and
> > > > depending in refresh rates the alerts will show up. Does this
> > happen
> > > > only for this rule or others as well?
> > > >
> > > > -------------------------
> >
> > > > Date: Tue, 24 Jun 2014 17:17:09 +0100
> > > > From: chas5873 () gmail com [5] [1]
> > > > To: snort-sigs () lists sourceforge net [6] [2]
> >
> > > > Subject: [Snort-sigs] Question regarding a rule
> > > >
> > > > Hi guys,
> > > >
> > > > Im having a bit of trouble with a rule that Im playing around
> > with
> > > > to detect torrent usage.
> > > >
> > > > alert tcp any any -> any any (msg: "P2P torrent metafile
> > download";
> > > > content:"|38 64 61|"; flow:established;
> > classtype:policy-violation;
> > > > sid:1000001; rev:1;)
> > > >
> > > > After examining the hex dumps from multiple torrents, I noticed
> > that
> > > > they all begin with 38 64 61, so thats where I managed to get
> > that
> > > > content from.
> > > >
> > > > When I run Snort and download the torrent though, it doesnt
> > alert
> > > > me straight away, however gives me about 20 alerts about 3 - 4
> > > > minutes later.
> > > >
> > > > Does anyone have any idea what could be causing this?
> > > >
> > > > Cheers,
> > > >
> > > > Charlie
> >
> > Also try detection_filtering your sid for testing:
> >
> > alert tcp any any -> any any (msg:"P2P torrent metafile download";
> > content:"|38 64 61|"; flow:established; classtype:policy-violation;
> > detection_filter: track by_dst, count 1, seconds 60; sid:1000001;
> > rev:1;)
> >
> > Ive seen cases where if too many alerts fire on the same content
> > they
> > wont all show up at the same time.
> >
> > James

No sweat..that happens.  I'm assuming that you killall -HUP snort to 
get the new rule with the detection filter yes?  How many alerts did you 
see in a minute?

James


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