[Snort-users] Snort rules maximum rules per file

Hussein Bahaidarah husseinb at ...11827...
Fri Jul 1 14:12:11 EDT 2011


no warning was displayed.
All rules are simple and of the following format:
alert tcp any any -> any 80 ( content:"URL"; react:; sid:1; )
The content is changed on every rule which is basically a URL and the SID is incremented from 1 to 942099
My system has 4GB memory. Before using snort 600MB is used and after snort full memory is utilized. That is on Now, I have switched to Version 2.9.1_beta as the "react" option was not firing on multiple rules.

I am testing snort with IXIA; but the result are not good as it seems that I am not configuring Snort in the right way. I need to achieve blocking for a big number of URL's with snort. Do you have any recommendations in this regards to tweak and optimize snort performance.


On Jun 29, 2011, at 7:52 PM, Russ Combs wrote:

We have kicked this around internally, and don't have a simple configuration suggestion to try so a few questions ...

Did you see any warnings in the startup output when you loaded 942099 rules?

What kind of rules are these?  Are they all very simple rules or rules with lots of options?

How much memory does your system have?  How much is used before and after starting Snort with all those rules?


On Sun, Jun 26, 2011 at 1:04 PM, Hussein Bahaidarah <husseinb at ...11827...> wrote:

I have found after extensive testing that only 131008 rules only fires alert and action. Any rule after that will not take any action.

On Jun 25, 2011, at 8:39 PM, Hussein Bahaidarah wrote:


Is there a limit on the number of rules support by snort in general? and on per file basis? I have customized a file with 942099 rules and it took about 15 minutes to start snort; but no alerts or actions wer fired.

Initializing rule chains...
942099 Snort rules read
    942099 detection rules
    0 decoder rules
    0 preprocessor rules
942099 Option Chains linked into 1 Chain Headers
0 Dynamic rules

+-------------------[Rule Port Counts]---------------------------------------
|             tcp     udp    icmp      ip
|     src       0       0       0       0
|     dst  942099       0       0       0
|     any       0       0       0       0
|      nc       0       0       0       0
|     s+d       0       0       0       0
Hussein Bahaidara

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