Snort rules are simply text files named by the convention RULETYPE.rules, e.g., web-attacks.rules or bleeding-web.rules. They are typically activated by including a reference to them in the snort.conf. First, include a directive in snort.conf telling Snort where to find the rules directory:
var RULE_PATH /nsm/rules/sensorname
Later in the snort.conf file, include references to the desired rules.
include $RULE_PATH/x11.rules
#include $RULE_PATH/icmp.rules
include $RULE_PATH/netbios.rules
In the example above this sensor will run x11.rules and netbios.rules, but not icmp.rules. Including BET rules is just as easy, with one twist. The snort.conf file would contain the following:
include /usr/local/etc/nsm/bleeding.conf
include $RULE_PATH/bleeding-attack_response.rules
include $RULE_PATH/bleeding-botcc.rules
include $RULE_PATH/bleeding-dos.rules
The first statement above points to a file called bleeding.conf that defines specific variables use by BET rules. At present it only has this entry:
var SSH_PORTS 22
This means BET rules where SSH_PORTS is mentioned translate that variable into meaning port 22.
Snort Report -- IDS Snort rules
Introduction
False positives
Sourcefire rules
Bleeding Edge Threats rules
Acquiring Snort rules
Activating Snort rules
Loading rules
About the author
Richard Bejtlich is founder of TaoSecurity, author of several books on network security monitoring, including Extrusion Detection: Security Monitoring for Internal Intrusions, and operator of the TaoSecurity blog.
