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

James Chase james at ...8230...
Fri Aug 28 11:26:41 EDT 2009


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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