[Snort-users] Snort home net and external net question

Andy Berryman aberryman at ...14765...
Fri Sep 3 14:50:28 EDT 2010


Now that's just a crazy idea. Why would someone RTFM? Much easier to be
lazy and ask. 

 

/sarcasm aside

 

 

So, if I'm reading it right, I need to do something like this:

 

HOME_NET [10.215.0.0/16,![10.215.40.0/24]]

EXTERNAL_NET !$HOME_NET

 

 

That would include all of the 10.215.x.x as the home net except
10.215.40.x would be excluded. So then the external net !$HOME_NET
should work. But it doesn't. 

 

It's too close to holiday weekend for me to be thinking like this, brain
usage stopped at 5pm Thursday. 

 

 

From: Joel Esler [mailto:jesler at ...1935...] 
Sent: Friday, September 03, 2010 12:42 PM
To: Andy Berryman
Cc: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Snort home net and external net question

 

Check out README.variables in the doc/ directory of the tarball.

 

 

On Sep 3, 2010, at 1:01 PM, Andy Berryman wrote:





I tried that, but am getting an error. I'm running 2.8.6.0

 

Sep  3 16:51:33 (none) snort[18415]: FATAL ERROR:
/snort/conf/general.rules(1) Negated IP ranges that are equal to or are
more general than non-negated ranges are not allowed.  Consider
inverting the logic: $EXTERNAL_NET.

 

var HOME_NET [10.215.0.0/16]

var EXTERNAL_NET [10.215.40.0/24,!$HOME_NET]

 

Is it b/c my home net is a /16 and the external net I'm trying to add is
a /24?

 

 

Thanks,

Andy

 

 

From: Joel Esler [mailto:jesler at ...1935...] 
Sent: Friday, September 03, 2010 11:53 AM
To: Andy Berryman
Cc: snort-users at lists.sourceforge.net
Subject: Re: [Snort-users] Snort home net and external net question

 

On Sep 3, 2010, at 11:01 AM, Andy Berryman wrote:






If I have my home net of snort set to:

 

var HOME_NET [10.215.0.0/16]

 

How can I make my external net be !$HOME_NET and 10.215.40.0/24 subnet?

 

 

With recent versions of Snort, you can do positives and negatives in the
same variable, but the more specific entry needs to come first.

 

var HOME_NET [10.215.0.0/16]

var EXTERNAL_NET [10.216.40.0/16,!$HOME_NET]

 

Should work.

 

Joel

 

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