Snort mailing list archives
Re: snort inline behavior
From: Stephan Scholz <sscholz () astaro com>
Date: Wed, 26 Nov 2003 10:04:07 +0100
If you add a QUEUE rule to iptables, you have to make sure that a process is actually listening to the ip_queue. Otherwise netfilter actually waits until a process picks up the packets. There is another issue. As soon as snort_inline has decided whether to drop or accept a packet, the following iptables rules are not being used anymore. The decision whether to accept or drop a packet is solely made in snort then. This way you can have the problem that your packet filter ruleset becomes ineffective. If you still have trouble with dropped connections, check the snort log file. The current ruleset is designed for intrusion *detection*, and if you changed all the rules to "drop", then you might drop harmless traffic, too. Stephan
First, thanks to all for the help on getting the right inline version running. I went through my firewall script and every '-j ACCEPT' I had, I changed to '-j QUEUE' and re-built my iptable chains. Did `insmod ip_queue`, loaded fine. Started up snort_inline with '-DQ -l ... -c ...'. Everything looked fine. After a couple of minutes I decided instead of -D (daemon) I'd rather see a little output to make sure it was seeing packets as expected. I was ssh'ed into the box so I figured my iptables "ESTABLISHED,RELATED -j QUEUE" entry should show a lot of ssh packets. I do a `kill` on the snort_inline pid and suddenly my ssh connection goes dead - I'm waiting for it to timeout now. In the mean time I've tried to re-ssh back into the box, but they just time out. I'm wondering if this is some weird deal that if you don't have someone running on QUEUE that the packets never get ACCEPTed and by shutting snort down I just shot myself in the foot. I'm going to go ahead and set up another box (that one is 1hr away, and the tech guy will arive in the morning and I'll walk him through changing QUEUE back to ACCEPT and restart the firewall...) and getting it tested locally where if it breaks I can fix it easily. In the mean time I was wondering if you guys could lend your experience here. Does killing snort_inline while it's watching the QUEUE break any connections that are getting -j QUEUEed? What happened here? Thanks!
-- Stephan Scholz <sscholz () astaro com> | Development Astaro AG | www.astaro.com | Phone +49-721-490069-0 | Fax -55 Visit Astaro at: - Infosecurity France, Paris, Nov. 26-27, 2003 Awards for ASL: - Linux Enterprise Readers' Choice Award: Best Firewall - October 2003 - LinuxWorld Product Excellence Award: Best Security Solution - August 2003 - "Excellent" Infoworld Magazine - August 2003 - "Four Stars" SC Magazine - June 2003 ------------------------------------------------------- This SF.net email is sponsored by: SF.net Giveback Program. Does SourceForge.net help you be more productive? Does it help you create better code? SHARE THE LOVE, and help us help YOU! Click Here: http://sourceforge.net/donate/ _______________________________________________ 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:
- Re: bad frag bits, (continued)
- Re: bad frag bits Brian (Nov 25)
- snort inline && current rules. /dev/null (Nov 25)
- Re: snort inline && current rules. Matt Kettler (Nov 25)
- Re: snort inline && current rules. /dev/null (Nov 25)
- Re: snort inline && current rules. Jeff Nathan (Nov 25)
- Re: snort inline && current rules. Matt Kettler (Nov 25)
- Re: snort inline && current rules. /dev/null (Nov 25)
- snort inline && current rules. /dev/null (Nov 25)
- Re: bad frag bits Brian (Nov 25)
- Re: snort inline && current rules. Josh Berry (Nov 25)
- snort inline behavior /dev/null (Nov 25)
- Re: snort inline behavior /dev/null (Nov 26)
- Re: snort inline behavior Stephan Scholz (Nov 26)
- Re: snort inline behavior /dev/null (Nov 26)
- Re: snort inline behavior Stephan Scholz (Nov 26)
- Re: snort inline behavior Josh Berry (Nov 26)