Modifying Detections with Rule Filters (Beta)

Overview

In the Panther Console, you can easily tune existing rules, including Panther-managed rules, by adding Rule Filters. Because Rule Filters are code-free, they expand who, on your security team, can contribute to detection fidelity. Note that Rule Filters are available only on rules, not scheduled rules nor policies.

Based on a detection's log type, you can select a field to filter on. From there, you will specify the operator and, if applicable, input a value. You can add filters while editing a rule, or directly from an associated alert. This quick tuning from alerts is particularly useful if the alert is a false positive, and you would like similar events in the future to not trigger the rule.

A common use case for filters is to add an allowlist or denylist.

How filters work

Filter statements are evaluated before a detection's rule function. A filter must return true (i.e., match the event) for the rule function, which is written in code, to then be run.

When multiple filters are included on one rule, they run using AND logic. OR statements are not supported.

If an event does not contain the field the filter is evaluating, the filter will pass. If the field the filter is evaluating has a value of none, the filter will return false on positive comparators or on comparators that don't apply, and true for inverse comparators.

Note that filters are not available during new rule creation. When you export a rule from the Panther Console, filters are not included.

How to add filters to a rule

You can add filters to a rule from its edit page, or within an alert triggered by that rule.

Add filters from an alert event

You can add Rule Filters to a rule directly from an event in an associated alert. This is particularly helpful if you've received a false positive alert, and want to tune the triggered detection so it won't match on similar events in the future.

1. Log in to the Panther Console.

2. In the left sidebar, click Alerts.

3. Locate the alert whose associated rule you'd like to tune, and click its name.

4. On the alert's detail page, scroll down to the Event section.

5. In the event's JSON, hover over the indicator you'd like the new filter to target, and click the target icon.

   • The Add Rule Filter panel will open on the righthand side of the window.

6. In the Add Rule Filter panel, a new filter will be pre-populated in the following way:

   • Field: defaults to the field on which you clicked the target icon in the event JSON.

   • Operator: defaults to is not, assuming you would not like to receive alerts for events like this in the future.

   • String: defaults to the value of the selected field in the event JSON.

7. Make any desired changes to the filter. All pre-populated fields (i.e., Field, Operator and String) are editable.

8. (Optional) Add more filters.

   1. At the bottom of the Add Rule Filter panel, click Close (or click outside of the panel).

   2. Repeat steps 5–7 above to add additional filters.

      • In the Filters section of the Add Rule Filter panel, previously added filters will be shown in addition to the new one you're adding.

      • You can continue adding filters to your rule in this fashion, but they are not saved until step 10, when you click Save & Run Test. (You can think of this like an online shopping cart.)

9. Locate the Unit Test section near the bottom of the panel. If the rule is not Panther-managed and you'd like to create a new unit test for the rule using the current event, click the checkbox labeled Add the current alert event as a unit test.

   • The toggle labeled The detection should trigger based on the example event is editable. It defaults to No, as you are likely trying to prevent alerts like this in the future.

   • If the rule is Panther-managed, this option will be greyed out.

10. Click Save & Run Test.

    • This runs all of the target rule's unit tests. If you created a new unit test in step 9, it is also run.

    • In order for the new filter(s) to be saved, all of the rule's unit tests must pass. If any of the unit tests fail:

      • If the rule is not Panther-managed, click View Detection to be taken to the rule's detail page to edit unit tests. From there, you can click Update to save your changes to the rule.

      • If the rule is Panther-managed, its unit tests are read-only, meaning you can't alter failing tests to make them pass. To be able to add the filter successfully, instead follow the Working with failed unit tests with filters workflow.

Add filters from a rule's edit page

1. In the left-hand navigation bar of your Panther Console, click Build > Detections.

2. In the list of detections, click a rule's name to view its details page.

3. In the Detect section, find the Filters tile, and on its right-hand side, click Add New.

4. In the Filters form, provide values for the Field, Operator, and if applicable, value(s).

   • Run the unit tests to ensure they pass with the added filter(s).

   • If the values(s) field takes in an array, see the Inputting array values instructions below.

5. In the upper-right corner of the page, click Update to save your changes.

Inputting array values

If the Rule Filter operator you've selected requires the value field to take in an array (such as the is in operator), you'll input the array values in a modal that pops up when you click into the value field.

To add values to an array:

1. After selecting a Field and Operator for your Filter, click into the values field.

   

   • This will open the array input modal.

2. In the modal, enter the array value(s) in the input field.

   • If your input is comma-delimited, check the Values entered above are comma-delimited checkbox.

     • When this field is checked, the text inputted into the values field will be separated (using a comma delimiter) into multiple values. For example, entering "User 1,User 2,User 3" will result in three values added.

       

   • If your input is not comma-delimited, leave Values entered above are comma-delimited unchecked.

     • When this field is unchecked, you can add values that contain commas one at a time. For example, entering "1,000" will add just one value.

3. Click Add.

4. Repeat steps 2-3 as needed, until all values have been added to the array.

5. Click Apply.

Working with failed unit tests with filters

For Panther-managed rules with filters, you currently cannot add or edit unit tests. You cannot save a rule if the unit test does not pass.

If a unit test fails, take the following steps:

1. Clone the Panther-managed rule.

2. Add your filter(s) to the cloned rule.

3. Edit the unit tests for the cloned rule so that they pass.

Rule filter reference

Refer to the below operators and value types when building out your filters.

Supported operators

Supported value types