Operational correlation rules

Operational correlation rules are used for working with active lists.

The correlation rule resource window contains the following configuration tabs:

• General—used to specify the main settings of the correlation rule resource. On this tab, you can select the type of correlation rule.
• Selectors—used to define the conditions that the processed events must fulfill to trigger the correlation rule. Available parameters vary based on the selected resource type.
• Actions—used to set the triggers that will activate when the conditions configured in the Selectors settings block are fulfilled. The Correlation rule resource must have at least one trigger. Available parameters vary based on the selected resource type.

General tab

• Name (required)—a unique name for this type of resource. Must contain from 1 to 128 Unicode characters.
• Tenant (required)—the tenant that owns the correlation rule.
• Type (required)—a drop-down list for selecting the type of correlation rule. Select operational if you want to create an operational correlation rule.
• Rate limit—maximum number of times a correlation rule can be triggered per second. The default value is 100.

  If correlation rules employing complex logic for pattern detection are not triggered, this may be due to the specific method used to count rule triggers in KUMA. In this case, try to increase the value of Rate limit to 1000000, for example.

• Description—the description of a resource. Up to 256 Unicode characters.

Selectors tab

There can be one selector in an operational resource. Only the Filter settings block is available in selector:

• Filter (required)—used to set the criteria for determining events that should trigger the selector. You can select an existing filter resource from the drop-down list, or select Create new to create a new filter.

  Creating a filter in resources

  1. In the Filter drop-down list, select Create new.
  2. If you want to keep the filter as a separate resource, set the Save filter toggle switch.

     In this case, you will be able to use the created filter in various services.

     The toggle switch is turned off by default.

  3. If you toggle the Save filter switch on, enter a name for the created filter resource in the Name field. The name must contain from 1 to 128 Unicode characters.
  4. In the Conditions settings block, specify the conditions that the events must meet:
     1. Click the Add condition button.
     2. In the Left operand and Right operand drop-down lists, specify the search parameters.

        Depending on the data source selected in the Right operand field, you may see fields of additional parameters that you need to use to define the value that will be passed to the filter. For example, when choosing active list you will need to specify the name of the active list, the entry key, and the entry key field.

     3. In the operator drop-down list, select the relevant operator.

        Filter operators

        • = – the left operand equals the right operand.
        • <—the left operand is less than the right operand.
        • <=—the left operand is less than or equal to the right operand.
        • >—the left operand is greater than the right operand.
        • >=—the left operand is greater than or equal to the right operand.
        • inSubnet—the left operand (IP address) is in the subnet of the right operand (subnet).
        • contains—the left operand contains values of the right operand.
        • startsWith—the left operand starts with one of the values of the right operand.
        • endsWith—the left operand ends with one of the values of the right operand.
        • match—the left operand matches the regular expression of the right operand. The RE2 regular expressions are used.
        • inActiveList—this operator has only one operand. Its values are selected in the Key fields field and are compared with the entries in the active list selected from the Active List drop-down list.
        • inCategory—the asset in the left operand is assigned at least one of the asset categories of the right operand.
        • inActiveDirectoryGroup—the Active Directory account in the left operand belongs to one of the Active Directory groups in the right operand.
        • TIDetect—this operator is used to find events using CyberTrace Threat Intelligence (TI) data. This operator can be used only on events that have completed enrichment with data from CyberTrace Threat Intelligence. In other words, it can only be used in collectors at the destination selection stage and in correlators.
     4. If necessary, select the do not match case check box. When this check box is selected, the operator ignores the case of the values.

        The selection of this check box does not apply to the InSubnet, InActiveList, InCategory or InActiveDirectoryGroup operators.

        This check box is cleared by default.

     5. If you want to add a negative condition, select If not from the If drop-down list.
     6. You can add multiple conditions or a group of conditions.
  5. If you have added multiple conditions or groups of conditions, choose a search condition (and, or, not) by clicking the AND button.
  6. If you want to add existing filters that are selected from the Select filter drop-down list, click the Add filter button.

     You can view the nested filter settings by clicking the button.

  Filtering based on data from the Extra event field

  Conditions for filters based on data from the Extra event field:

  • Condition—If.
  • Left operand—event field.
  • In this event field, you can specify one of the following values:
    • Extra field.
    • Value from the Extra field in the following format:

      Extra.<field name>

      For example, Extra.app.

      A value of this type is specified manually.

    • Value from the array written to the Extra field in the following format:

      Extra.<field name>.<array element>

      For example, Extra.array.0.

      The values in the array are numbered starting from 0.

      A value of this type is specified manually.

  • Operator – =.
  • Right operand—constant.
  • Value—the value by which you need to filter events.

Actions tab

There can be only one trigger in the operational resource kind: On every event. It is activated every time the selector triggers.

Available parameters of the trigger:

• Active lists update settings group—used to assign the trigger for one or more operations with active lists. You can use the Add active list action and Delete active list action buttons to add or delete operations with active lists, respectively.

  Available settings:

  • Name (required)—this drop-down list is used to select the Active list resources.
  • Operation (required)—this drop-down list is used to select the operation that must be performed:
    • Get—get the Active list entry and write the values of the selected fields into the correlation event.
    • Set—write the values of the selected fields of the correlation event into the Active list by creating a new or updating an existing Active list entry. When the Active list entry is updated, the data is merged and only the specified fields are overwritten.
    • Delete—delete the Active list entry.
  • Key fields (required)—this is the list of event fields used to create the Active list entry. It is also used as the Active list entry key.

    The active list entry key depends on the available fields and does not depend on the order in which they are displayed in the KUMA web interface.

  • Mapping (required for Get and Set operations)—used to map Active list fields with events fields. More than one mapping rule can be set.

    The left field is used to specify the Active list field. The middle drop-down list is used to select event fields. The right field can be used to assign a constant to the Active list field is the Set operation was selected.

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