Educause Security Discussion mailing list archives
writing SNORT rules
From: Peter Charbonneau <Peter.Charbonneau () WILLIAMS EDU>
Date: Tue, 2 Dec 2008 11:14:27 -0500
Good morning I have written 3 "quick and dirty" SNORT rules and am trying to follow the write/test/write/test/write/test/write/test Unfortunately even the first test isn't working. I never see the alert message for these rules in my alert log. Is there some other directive in the snort.conf file that could be precluding these stateless "hits" from being processed in some way? If you have any responses, we should probably take this off-line to keep the list from being clogged, unless, of course, this is a "class" problem for all first time rule writers. I think it's something stupid, but I just can't see it. These are the simplest rules I could think of with the ongoing process of modifying them for my final needs. My ultimate goal is to be able to grep the alert file for this LOCAL message and grab the timestamps; I want come up with a way to sanity check the duration of established ssh sessions to compare against host machine log files. Here are the rules: [root@netsniff emerging]# cat /usr/local/etc/rules/local.rules # $Id: local.rules,v 1.13 2005/02/10 01:11:04 bmc Exp $ # ---------------- # LOCAL RULES # ---------------- # alert tcp $EXTERNAL_NET any -> $NETSYS_NET $SSH_PORTS (flow:stateless; flags:S,12; msg: "LOCAL Connection attempt -- NetSys asset on port 22"; sid: 2008001;) alert tcp $EXTERNAL_NET any -> $NETSYS_NET $SSH_PORTS (flow:stateless; flags:F,12; msg: "LOCAL Connection termination -- NetSys asset on port 22"; sid: 2008002;) alert tcp $EXTERNAL_NET any -> $NETSYS_NET $SSH_PORTS (flow:stateless; flags:R,12; msg: "LOCAL Connection reset -- NetSys asset for port 22"; sid: 2008003;) [root@netsniff emerging]# The variables EXTERNAL_NET, NETSYS_NET, SSH_PORTS are all defined: var HOME_NET 137.165.0.0/16 var NETSYS_NET 137.165.224.0/24 var EXTERNAL_NET !$HOME_NET RULE_PATH is defined as var RULE_PATH /usr/local/etc/rules Here is the portion of the snort.conf file that "includes" the local.rules file: # # Please read the specific include file for more information and # README.alert_order for how rule ordering affects how alerts are triggered. #========================================= include $RULE_PATH/local.rules # include $RULE_PATH/bad-traffic.rules include $RULE_PATH/exploit.rules I have stopped and restarted snort with the same command line I always use: snort -A full -i eth3 -N -K none -c /usr/local/etc/snort.conf -D PeteC Peter Charbonneau Sr. Network and Systems Administrator Williams College (413) 597-3408 (office) (413) 822-2922 (cell)
Current thread:
- writing SNORT rules Peter Charbonneau (Dec 02)
- <Possible follow-ups>
- Re: writing SNORT rules Chris Green (Dec 02)
- Re: writing SNORT rules Peter Charbonneau (Dec 02)
- Re: writing SNORT rules Russell Fulton (Dec 02)