Snort mailing list archives
Re: HOME_NET not supporting multiple subnets?!
From: Erek Adams <erek () theadamsfamily net>
Date: Tue, 20 Aug 2002 01:20:26 -0700 (PDT)
On Tue, 20 Aug 2002, Jon Benson wrote: [...snip...]
There are just FAR too many alerts being logged and mostly false positives with the default setup. So I attempted to setup the HOME_NET appropriately.
Mmmmm.... I love the smell of false postives in the morning. ;-)
However it seems to me that it only uses the FIRST subnet when specifying more then one subnet. Eg. If HOME_NET were defined as: var HOME_NET [10.10.1.0/24, 10.10.2.0/24, 10.10.3.64/27, 10.10.4.1/27, 10.10.5.0/24] it would only generate alerts for packets destined for 10.10.1.0/24 reliably. There may be the odd packet that gets logged for the remaining subnets but it is definitely missing test traffic that I'm generating from an external network. Eg. wget "10.10.5.46/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%c1%1c ../winnt/system32/cmd.exe?/c+dir" fails to log an alert where as: wget "10.10.1.96/msadc/..%255c../..%255c../..%255c/..%c1%1c../..%c1%1c../..%c1%1c ../winnt/system32/cmd.exe?/c+dir" would log an alert as expected My problem is I have 10 different subnets I need to watch (real ones not the examples given) and the default of "any" is, as mentioned, far too noisy. Any/all suggestions would be most welcome.
Snort handles multi nets just fine. It's just not in your best interests to do so. :) This only applies (to my knowldege) to the 1.8 branch, but... Due to the way the rule lists are built, you'll get better performance with multiple instances. Cut down your subnets and you'll gain a measureable difference in perfomance. The more "unions" that exist, the work snort must do. Split your subnets into single instances if possible. At the very least run the more trafficed subnets alone, and the low bandwidth ones combined. Any little bit helps... :) Hope that helps! ----- Erek Adams Nifty-Type-Guy TheAdamsFamily.Net ------------------------------------------------------- This sf.net email is sponsored by: OSDN - Tired of that same old cell phone? Get a new here for FREE! https://www.inphonic.com/r.asp?r=sourceforge1&refcode1=vs3390 _______________________________________________ Snort-users mailing list Snort-users () lists sourceforge net Go to this URL to change user options or unsubscribe: https://lists.sourceforge.net/lists/listinfo/snort-users Snort-users list archive: http://www.geocrawler.com/redir-sf.php3?list=snort-users
Current thread:
- HOME_NET not supporting multiple subnets?! Jon Benson (Aug 19)
- Re: HOME_NET not supporting multiple subnets?! Erek Adams (Aug 20)