Snort mailing list archives

Re: Default rule set


From: Y M <snort () outlook com>
Date: Sun, 18 May 2014 07:42:22 +0000







From: Jake.Sallee () umhb edu
To: snort-users () lists sourceforge net
Date: Sun, 18 May 2014 05:44:22 +0000
Subject: [Snort-users]  Default rule set

Firstly, thank you all for the info, it has been very helpful.

I have configured my pulled pork with the security setting and it seems to be working well.  Now, as others have 
pointed out, configuring this setting in PP turns off all ET rules.  So my question is: are the rules turned on with 
the "security" setting in PP sufficient or should I augment them with rules from the ET set?

Setting the security policy in PulledPork does not actually turn ET ruleset off. It is just that ET rules does not have 
the "metadata" tag with the appropriate policy metadata info (balanced, security, etc...), hence PulledPork does not 
include or enable (uncomment) them in the augmented snort.rules file. For the second question, it largely depends on 
your environment and what are trying to protect. You can read more about what "security" or "connectivity" policies 
mean at the same link the Joel referred to: http://blog.snort.org/2013/10/snort-vrt-default-ruleset-rebalancing.html. 
Whether to augment ET rules or not, this again depends on your environment and your evaluation of the rules and what 
they can achieve to you in your environment. 
Also, a quick question about this suggestion:

2. Since PulledPork now processes modifysid.conf first (before enablesid.conf),
add pcre to modify ET rules to include the desired policy and PulledPork should
pick it up from there. I will need to re-test this one though.

Please forgive my inexperience but I am reading this statement two different ways:

1) Set PP with the security setting and use PCRE to enable ET rules in the modifysid.conf file
When PulledPork is configured to run the "security" policy (either in pulledpork.conf or in the command line), it will 
enable rules that are tagged with the security policy. Since ET does not have this metadata, they are not enable. 
Hence, modifying the enablesid.conf file. Meaning that either you enable rules by sid (GID:SID format) or by category 
(or even pcre) regardless of the policy used. The enablesid.conf has good documentation, I would suggest that you give 
that a read.
or
2) Use PCRE to enable the security sub-set of rules in modifysid.conf while PP is configured to use the ET rule set

The second case is to use PCRE to add the "security" metadata to the ET rules you want to be enabled in the 
modifysid.conf. In this case, PulledPork will see that these rules have the "security" metadata and will enable them in 
the next line of processing the rules. Like I said earlier, I will have to re-test this as this was sometime back and 
its blurry to me.
Which one is correct, or am I wrong on both counts?
See comments above. The end result is the same but
And lastly, if I do use some ET rules in conjunction with the security set of rules I will need to do some serious 
pruning to keep under the aforementioned 7,000 rule suggested limit. Are there any rules that duplicate effort in 
the ET and Security sets?  If so, is there an easy way to identify them and which one should I choose to use?

ET and VRT and two different entities with different approaches. There will be VRT and ET rules that match on the same 
traffic, even though they may have been written differently.
Thank you all again.

Jake Sallee
Godfather of Bandwidth
System Engineer
University of Mary Hardin-Baylor
WWW.UMHB.EDU

900 College St.
Belton, Texas
76513

Fone: 254-295-4658
Phax: 254-295-4221

________________________________________
From: waldo kitty [wkitty42 () windstream net]
Sent: Saturday, May 17, 2014 9:47 AM
To: snort-users () lists sourceforge net
Subject: Re: [Snort-users] Default rule set

On 5/17/2014 6:43 AM, Y M wrote:
 > ummm... does this "security", "balanced", "connectivity" stuff pertain to the ET
 > (EmergingThreats) rules sets?? ;)

I don't think ET ruleset has these policies.

exactly, thanks for confirming this, YM... it is especially important since the
OP's original question mentioned ET rules...

In the VRT ruleset, these are represented through the "metadata" tag with
options of "policy connectivity-ips", "policy balanced-ips", "policy
security-ips", and the most recent one "ruleset community". PulledPork use
these along with the "-I <policy>" to determine what rules to enable.

yes, this confirms the method with which the policy is determined... it is also
helpful for those who don't know or understand it...

During early tests, running PulledPork against both VRT and ET with a policy
specified, did not enable any ET rule. Two options to overcome this:
1. Add ET sids/categories into enablesid.conf, and PulledPork will enable them
regardless of policy specified, or (better)
2. Since PulledPork now processes modifysid.conf first (before enablesid.conf),
add pcre to modify ET rules to include the desired policy and PulledPork should
pick it up from there. I will need to re-test this one though.

ahh, very nice... i'm glad to see the PP has come such a long way in the short
time it has been available... excellent work by the maintainer! ;)

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