Recently, the Snort Rule Editor as a part of the Rules Management Interface has been updated. This redesign allows for increased flexibility and provides the user with more of a handle on the IPS rules settings.
How It Works
Entering the Rules Management Interface is easy and can be accessed from two possible locations. From the View Sensors page, the user can select the Edit Rules link to enter the Rules Management Interface. The user can also navigate to the Rules Management Interface from the Main Menu link.
Upon selecting the Rules Management Interface, the user will be prompted to select a sensor from the dropdown and then choosing the Load Rules button. From there, the user will be able to manage the rule sets on a sensor-by-sensor basis.
After selecting a sensor, the user will have the option to modify properties of the rule sets, and issue commands to the sensors with the tools on the Menu Bar. In order for the changes made in the rules interface to take effect, commit the changes using the Save button. (Please note that the Save/Cancel options only appear if the rules have been modified.) After selecting the Save option, a window will appear indicating that the changes are being verified. This process ensures that there are no issues with any changes that were made to the rule sets and that the sensor will correctly load the rules. Once the Save process is finished, the user will be prompted to reload the sensor.
To update the rule files, select the Get Updates button on the Snort Rules Controls. Most of the sensor controls buttons will be disabled/greyed out, and the Get Updates button will have a spinner icon until the update process finishes. Next, the page will refresh to indicate if the updates were applied successfully. After the Get Updates process completes, select to Save the changes and Reload the sensor configuration for the changes to take effect.
The Rule File List portion of the interface displays a complete listing of all the rule sets in the sensor configuration. The local.rules file contains the pass rules (if any) that have been generated using the Tune IDS feature and any rules that were uploaded by the user.
In the Rule List, each rule can be enabled or disabled by selecting the checkbox under the Active column next to each rule. If the checkbox under the Drop column next to a rule is checked, the sensor will drop flows that trigger the rule. Although we only recommend it for advanced users, each specific rule can also be edited by clicking on the rule itself. This will open the Rule Editor window, displaying the original rule, the editor, and some statistics that have been collected for that rule. Advanced Snort users can use the Rule Editor to make changes to the content of individual rules. When modifications are made, the Diff section will show changes to a rule since the most recent Save of the rule sets.
Pass Rules inform the IDS system that packet matching these rules should not generate alerts. These are helpful for eliminating false positives without having to disable the offending rule altogether. The Pass Rules have system-generated SIDs so that they do not conflict with the original rules that to which they refer. The user can utilize the tuning interface to add pass rules to the local.rules file. Please remember to Save any changes to the rule sets through the Rules Management Interface.
For users that want to run a reduced rule set for performance reasons, there is an Automatic Tuning option under the Bulk Edit menu. This option will disable rules that are unlikely to trigger based on our observations across all customer networks. After clicking on the Automatic Tuning option, the changes will be merged with any prior changes that have made, meaning that rules that have specifically enabled will stay enabled. If the user wants to revert to a default minimal set, they should consider first using the Rules Defaults option. Once the Automatic Tuning has processed the rules, it will then automatically fetch the latest updates and disable all of the appropriate rules. To complete this process, the user will need to select Save so that the changes are committed.
Full color images and even more detailed instructions regarding The Rules Management Interface can found in the MetaFlows Wiki.