When Snort is started, its output reveals several clues regarding the rules it recognizes.
Here we see Snort recognizing the snort.conf file as containing rules, thereby triggering IDS mode.
Mar 20 16:59:26 cel433 snort: Parsing Rules file /usr/local/etc/nsm/snort.conf
Here Snort recognizes a RULE_PATH, meaning the actual rules we're using will be found (assuming they live in the directory specified).
Mar 20 16:59:26 cel433 snort:Var 'RULE_PATH' defined, value len=17 cha
Mar 20 16:59:26 cel433 snort: , value = /nsm/rules/cel433
When run in the foreground, Snort reports the number of rules loaded. This information does not appear when Snort is run as a daemon and messages are sent to /var/log/messages, as was the case with the previous message examples. The following shows Snort recognized 8352 rules when Snort is run in the foreground.
8352 Snort rules read...
8352 Option Chains linked into 680 Chain Headers
Stay tuned for a future Snort Report on rules and rule management.
Snort Report -- IDS Snort rules
Bleeding Edge Threats rules
Acquiring Snort rules
Activating Snort 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.