[Snort-users] Snort with two sniffing interfaces

Edward Bjarte Fjellskål edward.fjellskal at ...14590...
Thu May 20 03:24:43 EDT 2010


Crook, Parker wrote:
> Either run two instances:
> 
> /snort/snort -D -N -i eth0 -c /snort/conf/snort.conf
> 
> /snort/snort -D -N -i eth1 -c /snort/conf/snort.conf
> 
>  
> 
>  or bond the interfaces:
> 
> /snort/snort -D -N -i bond0 -c /snort/conf/snort.conf
> 
>  
> 
> Personally I run two instances because I have two logically different
> environments I am sniffing and want/need to run two different configs;
> if I didn’t have this need I would probably go the bonded route.

Hi,

I Just wanted to add the little talked about feature of snort, where
you can define virtual networks, example:

config binding: /etc/snort/vips/snort-0.conf net 192.168.0.0/24
config binding: /etc/snort/vips/snort-1.conf net 192.168.1.0/24
config binding: /etc/snort/vips/snort-2.conf net 192.168.2.0/24

So, you have a default /etc/snort/snort.conf and configure that as
a fall-back configuration (Catch all traffic not handled by your
virtual configs) and then add the statements above. You can then
configure snort-0.conf, snort-1.conf, snort-2.conf to handle their
respective traffic (Variables, rules, preprocessors etc).

In this case, if you have:
192.168.0.0/24 on eth1
192.168.1.0/24 on eth2
192.168.2.0/24 on eth3

you would need to bond them together and have snort listen on the bonded
interface.

My gut feelings are that there are some performance and memory benefits
firing up one instance of snort configured with virtual-networks, then
firing up X instances of snort, but I have not done any tests.
*I would like to hear thoughts from other playing with this feature*

Best regards,
Edward Fjellskål


>  
> 
> -Parker
> 
>  
> 
> ------------------------------------------------------------------------
> 
> *From:* Andy Berryman [mailto:aberryman at ...14765...]
> *Sent:* Tuesday, May 18, 2010 1:11 PM
> *To:* snort-users at lists.sourceforge.net
> *Subject:* Re: [Snort-users] Snort with two sniffing interfaces
> 
>  
> 
> So, if you want to use snort to sniff on two interfaces, how do you use
> the same config file? Is that possible?  Or should I just bond them and
> make snort listen on the bonded interface?
> 
>  
> 
> When I try it like this, I get errors b/c of the .so rules.
> 
>  
> 
> /snort/snort -D -N -i eth0 -i eth1 -c /snort/conf/snort.conf
> 
>  
> 
> May 18 17:05:54 (none) snort[14547]: FATAL ERROR:
> /snort/conf/snort.rules(46) : pcre compile of
> "(<object\s*[^>]*\s*id\s*=\s*(?P<m13>\x22|\x27|)(?P<id1>.+?)(?P=m13)(\s|>)[^>]*\s*classid\s*=\s*(?P<q27>\x22|\x27|)\s*clsid\s*\x3a\s*{?\s*77829F14-D911-40FF-A2F0-D11DB8D6D0BC\s*}?\s*(?P=q27)(\s|>).*(?P=id1)\s*\.\s*(SetFormatLikeSample|CreateFile)|<object\s*[^>]*\s*classid\s*=\s*(?P<q28>\x22|\x27|)\s*clsid\s*\x3a\s*{?\s*77829F14-D911-40FF-A2F0-D11DB8D6D0BC\s*}?\s*(?P=q28)(\s|>)[^>]*\s*id\s*=\s*(?P<m14>\x22|\x27|)(?P<id2>.+?)(?P=m14)(\s|>).*(?P=id2)\.(SetFormatLikeSample|CreateFile))\s*\("
> failed at offset 30 : unrecognized character after (?
> 
>  
> 
> Thanks,
> 
> Andy Berryman
> 
>  
> 
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>  
> 
> 
> ------------------------------------------------------------------------
> 
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> 
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