[Snort-users] Filtering the Snort Rule Set for Firewall Blocks

CunningPike cunningpike at ...11827...
Fri Aug 28 16:54:56 EDT 2009


We ran our sensor for quite a while before we started using snortsam so we
could get a feel for which rules would be good block candidates - I would
advise you to do the same.

The Emerging Threats project (http://www.emergingthreats.net/) has a couple
of block rulesets that block known RBN hosts and so forth - they might be a
good start for snortsam, but be aware that they are IP-based rules and can
be quite processor intensive. You might find the IP blacklist beta code for
snort of more interest in this area.

CP

On Fri, Aug 28, 2009 at 8:26 AM, James Chase <james at ...8230...>wrote:

> Hi,
>
> I have recently setup a Snort sensor and am using snortsam with barnyard
> connected to an openBSD firewall to dynamically block IP's that trigger
> subsets of rules in snort.
>
> My question is what is the best way to sort out a good rule set for our
> environment? Is there a general list of known rules that are always bad
> traffic that people are using, or is it really just watching the IDS
> everyday and adding alerts that appear to be malicious and removing
> those that seem to alert on legitimate traffic? I notice a lot of rules
> have very general triggers, like accessing any page with calendar.php in
> it, and I notice that if the system we have setup were in production
> there would be a lot of good traffic being blocked.
>
> And is anyone else using a setup with snort adding blocks on the
> firewall, and if so what is your setup like, how long do you block
> traffic for, and how do you mitigate the risk of blocking legitimate
> users for applications where the source IP's are dynamic.
>
> Thanks for any feedback,
> James
>
>
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