Re: IP Protocol Rules?

[Joel Esler <jesler () sourcefire com>]

I'd suggest a review of the code then. (As you are doing). The list isn't accustomed to doing other's homework. 

--
Joel Esler
Senior Research Engineer, VRT
OpenSource Community Manager

On Jul 2, 2012, at 10:01 PM, jorbru30 () comcast net wrote:

> Thank you very much everyone for the detailed response. 
> I am trying to understand snort performance details for a school project. 
> Thanks!
> Jorda.
> From: "Joel Esler" <jesler () sourcefire com>
> To: "Livio () metaflows com" <livio () metaflows com>
> Cc: snort-devel () lists sourceforge net
> Sent: Sunday, July 1, 2012 3:30:13 PM
> Subject: Re: [Snort-devel] IP Protocol Rules?
>
> IP rules are evaluated against all protocols.  If you can specify tcp or udp, that's obviously the better idea.  
> People insist on writing IP rules, but as someone else in this thread already pointed out, these rules are bad 
> performers.
>
> What are you trying to accomplish?
>
> -- 
> Joel Esler
>
> On Sunday, July 1, 2012 at 6:01 PM, Livio () metaflows com wrote:
>
> I woul talk to silicom. They are cheaper 82599s and come with a prepaid dna license. You can't go wrong..
> -- 
> Sent from my Android phone with K-9 Mail. Please excuse my brevity.
>
> Joshua Kinard <kumba () gentoo org> wrote:
> On 07/01/2012 4:04 PM, Tony Robinson wrote:
> > IP protocol rules are rules that trigger against IP traffic. In the
> > standard snort rule header, you can specify a rule function
> > [Alert/Pass/Drop], a protocol, [TCP/UDP/ICMP/IP], network or address 1
> > [address/IPvar], source port [port/icmp code], where the traffic flows
> > [direction], network or address 2 [address/IPvar], destination port
> > [port/icmp code].
> >
> > IP Protocol rules are simply rules that trigger against rule content with
> > IP chosen as the protocol. If IP is chosen as the protocol you cannot
> > specify a port or an ICMP code. Snort will do content matching against ALL
> > IP packets. The rule header for an IP rule will usually look something like
> > this:
> >
> >
> > alert ip [address 1] any -> [address 2] any [rule content
> goes here]
> > If you want to see an example of an IP protocol rule, take a look at rule
> > 18997
> >
> > http://www.snort.org/search/sid/18997?r=1
> >
> > it's a rule that alerts against IP protocol traffic and has a specific
> > content match. The other use case for IP rules is to block traffic from
> > certain IP addresses when we don't know the content, or more than one type
> > of protocol may be used to communicate. This rules aren't very good
> > performers, but will do in a pinch if you know, say, the ip address of a
> > known CNC server and just want to alert against any traffic going to/from
> > that ip address.
> >
> > sids 20523 and 20524 are examples of this -- blocking known ip addresses
> > for Duqu CNC hosts.
> >
> > Hope this answers the question.
> >
> > -Tony
>
> I'll add
> that IP protocol rules also make use of the "ip_proto" keyword.
> You usually want to put this keyword into any "alert ip" rule, as Snort's
> fast-pattern matcher will use the protocol number as the "destination port"
> to prime the fp algorithm to quickly judge which packets to keep for further
> inspection.
>
> I.e., if you wanted to alert on SCTP traffic containing the string "foobar":
> alert ip any any -> any any (msg:"SCTP Traffic"; ip_proto:132;
> content:"foobar"; nocase; sid:123456789; rev:1; classtype:misc-activity;)
>
> You have to be VERY careful with IP proto rules.  They can quickly bring
> Snort to its knees if used incorrectly.
>
> -- 
> Joshua Kinard
> Gentoo/MIPS
> kumba () gentoo org
> 4096R/D25D95E3 2011-03-28
>
> "The past tempts us, the present confuses us, the future frightens us.  And
> our lives slip away, moment by moment, lost in that vast, terrible in-between."
>
> --Emperor Turhan,
> Centauri Republic
>
>
>
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