Re: system setup for SNORT: looking for recommendation

["AJ Butcher, Information Systems and Computing" <Alex.Butcher () bristol ac uk>]

--On 28 May 2004 16:36 -0400 "Jeff Schmidt (CACL Tech Asst)" 
<schmidje () oplin org> wrote:

> Hello,
>    I'm setting up a pc with OpenBSD for the purpose of using it as an
> NIDS system with SNORT. I've been reading a lot of documentation, but
> here are a few questions that I have not come across answers to:
>
> Realistic system requirements: We are trying to do ID on a network with
> about 2 dozen computers, so it's not a huge network. However, being at a
> public library, each of the individual computers does get quite a bit of
> traffic. How much disk space should I set aside for SNORT to record data
> about network activity? And under what filesystem? It appears that SNORT
> basically saves it's logs and data in /var/log/snort, so I'm guessing I
> want to partition my hard drive so that /var has most of the available
> space? The server currently has 128MB ram - is this sufficient? It has a
> PII-400Mhz processor - is that fast enough to do the real-time analysis
> of network traffic that is necessary?

To give you a performance point, I've currently got snort monitoring a link 
that peaks at around 45Mbits/s for a few hours each day with 0% packet 
loss.  I'm using nearly the entire rule set. Snort's logging anywhere from 
20 to 80 alerts/s. MySQL and ACID are running on the same host (for now, at 
least).

And I'm doing this all on a single processor P4 1.7GHz with 512M of memory 
and a single IDE disc.

I'm using Linux, rather than BSD. I haven't had to do much in the way of 
performance tweaks:

- enable IDE DMA
- mount /var with noatime flag
- increase amount of memory allocated to MySQL
- use one of the spool processors between snort and the database (i.e. 
mudpit, barnyard or FLoP - I use mudpit for now)
- compile snort with Phil Wood's modified libpcap which uses Linux's mmap 
mode for packet capture.

Ultimately, the power you require will be a function of

a) the number of rules you have enabled
b) the volume and rate of traffic
c) the number of concurrent sessions

> Jeff Schmidt

Best Regards,
Alex.
--
Alex Butcher: Security & Integrity, Personal Computer Systems Group
Information Systems and Computing             GPG Key ID: F9B27DC9
GPG Fingerprint: D62A DD83 A0B8 D174 49C4 2849 832D 6C72 F9B2 7DC9




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