[Snort-users] Certin ET rulesets and 100 percent usage.

Matt Jonkman jonkman at ...4024...
Fri May 8 09:22:11 EDT 2009


Quick question for you Marty. Eion and Joel Esler both have made the
point that if we split the IP matching rules from a single "alert ip "
into two "alert tcp" and "alert udp" we'll get a significant performance
increase. (which I'm implementing today)

I know we'll miss icmp then, but that's not a big deal. But what causes
the performance gain here? Doesn't make sense on the surface.

Thanks!

Matt

Martin Roesch wrote:
> Yeah, you're hitting the rule chains iteratively and that's just not
> going to perform.  If you want to filter large sets of IP addresses
> that would be more properly implemented as a preprocessor with
> dedicated functionality.
> 
> Marty
> 
> On Thu, May 7, 2009 at 12:15 PM, Matt Jonkman <jonkman at ...4024...> wrote:
>> Straight IP matching is something Snort doesn't do well. Unfortunately.
>> So this isn't that unexpected.
>>
>> I'd only run those rulesets where you can afford the cycles. or run a
>> second snort for these alone and turn off everything in it's config to
>> streamline some.
>>
>> Matt
>>
>> jlay at ...13475... wrote:
>>> So here's something interesting.  Enabling ANY of the below rulesets
>>> results in snort using 100% CPU:
>>>
>>> emerging-botcc.rules
>>> emerging-compromised.rules
>>> emerging-drop.rules
>>> emerging-dshield.rules
>>> emerging-rbn.rules
>>> emerging-tor.rules
>>>
>>> Without snort uses around 49%.  Using 2.8.4.1 with about 700K average
>>> traffic.  Any thoughts?  Thanks.
>>>
>>> James
>>>
>>>
>>>
>>>
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>> --
>> --------------------------------------------
>> Matthew Jonkman
>> Emerging Threats
>> Phone 765-429-0398
>> Fax 312-264-0205
>> http://www.emergingthreats.net
>> --------------------------------------------
>>
>> PGP: http://www.jonkmans.com/mattjonkman.asc
>>
>>
>>
>> ------------------------------------------------------------------------------
>> The NEW KODAK i700 Series Scanners deliver under ANY circumstances! Your
>> production scanning environment may not be a perfect world - but thanks to
>> Kodak, there's a perfect scanner to get the job done! With the NEW KODAK i700
>> Series Scanner you'll get full speed at 300 dpi even with all image
>> processing features enabled. http://p.sf.net/sfu/kodak-com
>> _______________________________________________
>> Snort-users mailing list
>> Snort-users at lists.sourceforge.net
>> Go to this URL to change user options or unsubscribe:
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> 
> 
> 

-- 
--------------------------------------------
Matthew Jonkman
Emerging Threats
Phone 765-429-0398
Fax 312-264-0205
http://www.emergingthreats.net
--------------------------------------------

PGP: http://www.jonkmans.com/mattjonkman.asc






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