Filters

Filters let you select events based on specified conditions.

The collector service uses filters to filter out events that you do not want to send to KUMA. That is, an event that matches the filter condition is NOT sent to KUMA.

Filters can be used in the following KUMA services and features:

• Collector.
• Correlator.
• Storage.
• KUMA agents.
• Correlation rules.
• Enrichment rules.
• Aggregation rules.
• Destinations.
• Response rules.
• Segmentation rules.

You can use standalone filters or built-in filters that are stored in the service or resource where they were created.

For these resources, you can enable the display of control characters in all input fields except the Description field.

Available settings for filters:

• Name (required)—a unique name for this type of resource. Must contain 1 to 128 Unicode characters. Inline filters are created in other resources or services and do not have names.
• Tenant (required)—name of the tenant that owns the resource.
• Description—up to 4,000 Unicode characters describing the filter.
• The Conditions group of settings lets you formulate filtering criteria by creating filter conditions and groups of filters, or by adding existing filters.

  To create filtering criteria, you can use builder mode or source code mode. The builder mode is used by default.

  In builder mode, you can create or edit filter criteria by selecting filter conditions and operators from drop-down lists.

  In source code mode, you can use text commands to create and edit search queries.

  You can freely switch between modes when creating filtering criteria. To switch to source code mode, click the Code button. When switching between modes, the created condition filters are preserved. If the filter code is not displayed on the Code tab after linking the created filter to the resource, go to the Builder tab and then go back to the Code tab. The filter code is displayed.

Creating conditions in builder mode

You can create filtering criteria in builder mode using the following buttons:

• Add condition adds a string with fields for defining a condition.
• Add group adds a group of filters. Group operators can be switched between AND, OR, and NOT. You can add groups, conditions, and existing filters to groups of filters. Conditions placed in the NOT subgroup are combined with the AND operator.

To replace an operator in the created condition, click the operator that you want to replace and select the new operator from the drop-down list.

To delete an operator in the created condition, click the operator that you want to delete and press Backspace.

To alter the sequence of filter conditions, click and drag and drop the condition to the new location.

Conditions, groups, and filters can be deleted by using the button.

Settings of conditions:

• When (required)—in this drop-down list, you can specify whether or not to use the inverted function of the operator.
• Left operand and Right operand (required)—used to specify the values that the operator will process. The available types depend on the selected operator.

  Operands of filters

  • Event field—used to assign an event field value to the operand. Advanced settings:
    • Event field (required)—this drop-down list is used to select the field from which the value for the operand should be extracted.
  • Active list—used to assign an active list record value to the operand. Advanced settings:
    • Active list (required)—this drop-down list is used to select the active list.
    • Key fields (required)—this is the list of event fields used to create the Active list entry and serve as the Active list entry key.
    • Field (required unless the inActiveList operator is selected)—used to enter the Active list field name from which the value for the operand should be extracted.
  • Context table—used to assign a context table value to the operand. Advanced settings:
    • Context table name (required)—this drop-down list is used to select a context table.
    • key fields (required)—a list of event fields or local variable that are used to create a context table record and serve as the key for the context table record.
    • field—used to enter the name of the context table field from which the operand value must be extracted.
    • index—used to enter the index of the list field of the table from which the operand value must be extracted.
  • Dictionary—used to assign a dictionary resource value to the operand. Advanced settings:
    • Dictionary (required)—this drop-down list is used to select the dictionary.
    • Key fields (required)—this is the list of the event fields used to form the dictionary value key.
  • Constant—used to assign a custom value to the operand. Advanced settings:
    • Value (required)—here you enter the constant that you want to assign to the operand.
  • Table—used to assign multiple custom values to the operand. Advanced settings:
    • Dictionary (required)—this drop-down list is used to select a Table-type dictionary.
    • Key fields (required)—this is the list of the event fields used to form the dictionary value key.
  • List—used to assign multiple custom values to the operand. Advanced settings:
    • Value (required)—here you enter the list of constants that you want to assign to the operand. When you type the value in the field and press ENTER, the value is added to the list and you can enter a new value.
  • TI—used to read the CyberTrace threat intelligence (TI) data from the events. Advanced settings:
    • Feed (required)—this field is used to specify the CyberTrace threat category.
    • Key fields (required)—this drop-down list is used to select the event field containing the CyberTrace threat indicators.
    • Field (required)—this field is used to specify the CyberTrace feed field containing the threat indicators.
• Operator (required)—used to select the condition operator.

  In this drop-down list, you can select the do not match case check box if the operator should ignore the case of values. This check box is ignored if the inSubnet, inActiveList, inCategory, InActiveDirectoryGroup, hasBit, inDictionary operators are selected. This check box is cleared by default.

  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.
  • hasBit—checks whether the left operand (string or number) contains bits whose positions are listed in the right operand (in a constant or in a list).

    The value to be checked is converted to binary and processed right to left. Chars are checked whose index is specified as a constant or a list.

    If the value being checked is a string, then an attempt is made to convert it to integer and process it in the way described above. If the string cannot be converted to a number, the filter returns False.

  • hasVulnerability—checks whether the left operand contains an asset with the vulnerability and vulnerability severity specified in the right operand.

    If you do not specify the ID and severity of the vulnerability, the filter is triggered if the asset in the event being checked has any vulnerability.

  • 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.
  • inDictionary—checks whether the specified dictionary contains an entry defined by the key composed with the concatenated values of the selected event fields.
  • 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.
  • inContextTable—presence of the entry in the specified context table.
  • intersect—presence in the left operand of the list items specified in the right operand.

The available operand kinds depends on whether the operand is left (L) or right (R).

Available operand kinds for left (L) and right (R) operands

You can use hotkeys when managing filters. Hotkeys are described in the table below.

Hotkeys and their functions

The usage of extended event schema fields "string", "number", or "float" types is the same as the usage of fields of the KUMA event schema.

When using filters with extended event schema fields of the "Array of strings", "Array of numbers", and "Array of floats" types, you can use the following operations:

• The "contains" operation returns True if the specified substring is present in the array, otherwise it returns False.
• The "match" operation matches the string against a regular expression.
• The "intersec" operation.

Creating conditions in source code mode

The code editor mode allows you to quickly edit conditions, select and copy blocks of code.

On the right side of the builder, you can find the navigator, which lets you to navigate the filter code.

Line wrapping is performed automatically at AND, OR, NOT logical operators, or at commas that delimit the items in the list of values.

Names of resources used in the filter are automatically specified. Fields containing the names of linked resources cannot be edited. The names of shared resource categories are not displayed in the filter if you do not have the "Access to shared resources" role. To view a list of resources for the selected operand inside an expression, press Ctrl+Space. This displays a list of resources.

The filters listed in the table below are included in the KUMA kit.

Predefined filters