Re: Question regarding a rule

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

On 2014-06-24 13:01, Charlie Egan wrote:
> By killall -HUP Im guessing thats just a command to kill the Snort
> process? Ive been using the command service snort reload in between
> modifying rules, its definitely detected the changes to the rule.
>
> 25 alerts have been coming through within the space of about 4 
> seconds
> and thats it, theres no more after that - this happens about 3 
> minutes
> ish after Ive downloaded a torrent file onto my desktop.
>
> Apologies if Ive got any of the above wrong about the killall -HUP, 
> Im
> still a beginner with Snort so have a lot of learning to be done!
>
> Cheers
>
>  On Tue, Jun 24, 2014 at 7:03 PM, James Lay <jlay () slave-tothe-box net
> [13]> wrote:
>
> > 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 [1]
> >
> > > [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 [2] [1]
> > > > > To: snort () outlook com [3] [2]
> > > > > CC: snort-sigs () lists sourceforge net [4] [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 [5] [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 [6] [5] [1]
> > > > > > To: snort-sigs () lists sourceforge net [7] [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;)

Ok...can you post about 5 of these from your .fast file?  Make sure to 
obfuscate anything sensitive that you don't want the world to see :D

James

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