Rule exceptions and value listsedit

To prevent the creation of unwanted alerts, you can add exceptions to any rule. Exceptions contain the source event conditions that determine when alerts are not generated. They provide a convenient way of allowing trusted processes and network activity to function without producing unnecessary noise.

You can add multiple exceptions to one rule.

When you add an exception to the Elastic Endpoint Security rule, you can select to add the exception to the Endpoint. When selected, the exception is added to both the detection rule and the Elastic Endpoint agent on your hosts.

In addition to defining exception queries for source event values, rule exceptions can be used with value lists. Value lists are lists of items with the same Elasticsearch data type. You can create value lists with these types:

  • keyword (many ECS fields are keywords)
  • ip
  • ip_range
  • text

After creating value lists, you can use is in list and is not in list operators to define exceptions.

Create and manage value listsedit

To create a value list to use with exceptions:

  1. Prepare a txt or csv file with all the values you want to use for determining exceptions from a single list. If you use a txt file, new lines act as value delimiters.

    All values in the file must be of the same Elasticsearch type.

  2. Go to DetectionsManage detection rules.
  3. Click Upload value lists. The Upload value lists window opens.

    upload lists ui
  4. Select the list type (Keywords, IP addresses, IP ranges, or Text) from the Type of value list drop-down.
  5. Drag or select the csv or txt file that contains the values.
  6. Click Upload list.

When the name of the file you are uploading already exists, the values in the new file are appended to the previously uploaded values.

To view, delete, or export existing value lists:

  1. Go to DetectionsManage detection rules.
  2. In the Value lists table, click the required action button.
manage value list

Add exceptions to a ruleedit

You can add exceptions to a rule via the Rule details page or the Alerts table. When you add an exception, you can also close all alerts that meet the exception’s criteria.

Be careful when adding exceptions to event correlation rules. Exceptions are evaluated against every event in the sequence, and when the exception matches any event(s) in the sequence, alerts are not generated. To exclude values from a specific event in the sequence, update the rule’s EQL statement. For example:

`sequence
  [file where file.extension == "exe"
  and file.name != "app-name.exe"]
  [process where true
  and process.name != "process-name.exe"]`
  1. To add an exception via the Rule details page:

    1. Go to the Rule details page of the rule to which you want to add the exception (DetectionsManage detection rules → <rule name>).
    2. Scroll down to the Trend histogram and select the Exceptions tab.

      exception histogram
    3. Click Add new exception.
  2. To add an exception via the Alerts table:

    1. Select the Detections tab.
    2. Scroll down to the Alerts table and click the More Actions button (…​), then select Add rule exception.

      more action button

      The Add Rule Exception window opens (via the Alerts table).

      add exception ui
  3. Add conditions that define when the exception prevents alerts. You can define multiple conditions with OR and AND relationships. In the example above, the exception prevents the rule from generating alerts when the svchost.exe process runs on agent hostname siem-kibana.

    You can use nested conditions. However, this is only required for these fields. For all other fields, nested conditions should not be used.

    If you have created value lists, you can use them to exclude or include all values in a list with is in list and is not in list operators:

    exceptions ui list

    When using a list, all exception statements must use is in list and is not in list operators.

  4. You can select any of the following:

    • Close this alert: Closes the alert when the exception is added. This option is only available when adding exceptions via the Alerts table.
    • Close all alerts that match this exception and were generated by this rule: Closes all alerts that match the exception’s conditions and were generated only by the current rule.
  5. Click Add Rule Exception.

Add Elastic Endpoint Security exceptionsedit

Like detection rule exceptions, you can add Endpoint agent exceptions via both the Elastic Endpoint Security rule and its generated alerts. Alerts generated from the Elastic Endpoint Security rule have the following fields:

  • signal.original_event.module determined:endpoint
  • signal.original_event.kind:alert

Additionally, you can add Endpoint exceptions via rules that are associated with Elastic endpoint rule exceptions. To associate rules, when creating or editing a rule select the Elastic endpoint exceptions option.

Exceptions added to the Elastic Endpoint Security rule affect all alerts sent from the Endpoint agent. Be careful not to unintentionally prevent some Endpoint alerts.

  1. To add an Endpoint exception via the Rule details page:

    1. Go to the Rule details page and select the Elastic Security Endpoint rule (DetectionsManage detection rulesElastic Endpoint Security).
    2. Scroll down to the Trend histogram and select the Exceptions tab.
    3. Click Add Endpoint exception.
  2. To add an exception via the Alerts table:

    1. Select the Detections tab.
    2. Scroll down to the Alerts table, and from an Elastic Security Endpoint alert, click the More actions button (…​), then select Add Endpoint exception.

      The Add Endpoint Exception window opens (via the Alerts table).

      endpoint add exp
  3. If required, modify the conditions.

    Exceptions with nested conditions describes when nested conditions are required.

  4. You can select any of the following:

    • Close this alert: Closes the alert when the exception is added. This option is only available when adding exceptions via the Alerts table.
    • Close all alerts that match this exception, including alerts generated by other rules: Closes all alerts that match the exception’s conditions.
  5. Click Add Exception.

    An exception is created for both the detection rule and the Elastic Endpoint agent.

Exceptions with nested conditionsedit

Some Endpoint objects contain nested fields, and the only way to ensure you are excluding the correct fields is with nested conditions. One example is the process.Ext object:

{
  "ancestry": [],
  "code_signature": {
    "trusted": true,
    "subject_name": "LFC",
    "exists": true,
    "status": "trusted"
  },
  "user": "WDAGUtilityAccount",
  "token": {
    "elevation": true,
    "integrity_level_name": "high",
    "domain": "27FB305D-3838-4",
    "user": "WDAGUtilityAccount",
    "elevation_type": "default",
    "sid": "S-1-5-21-2047949552-857980807-821054962-504"
  }
}

code_signature.subject_name refers to the process signature not the process name.

Only these objects require nested conditions to ensure the exception functions correctly:

  • Endpoint.policy.applied.artifacts.global.identifiers
  • Endpoint.policy.applied.artifacts.user.identifiers
  • Target.dll.Ext.code_signature
  • Target.process.Ext.code_signature
  • Target.process.Ext.token.privileges
  • Target.process.parent.Ext.code_signature
  • Target.process.thread.Ext.token.privileges
  • dll.Ext.code_signature
  • file.Ext.code_signature
  • file.Ext.macro.errors
  • file.Ext.macro.stream
  • process.Ext.code_signature
  • process.Ext.token.privileges
  • process.parent.Ext.code_signature
  • process.thread.Ext.token.privileges

Nested condition exampleedit

Creates an exception that excludes all LFC-signed trusted processes:

nested exp

View and manage Exception listsedit

The Exception lists table enables you to view and manage all exceptions that have been assigned to rules. To view the Exception lists table, go to DetectionsManage detection rules, then select the Exception Lists tab.

exception list

The table displays each Exception list on an individual row, with the most recently created list at the top. Each row contains information such as the number and name of rule(s) the Exception list is assigned to, the name of the rule(s) assigned to the Exception list, the date the list was created, last edited, and options to export or delete it.

To view details of the rule the Exception list is assigned to, click the link in the Rules assigned to column.

To filter Exception lists by a specific value, enter a query in the Search bar. You can search the following attributes:

  • name
  • list_id
  • created_by
  • type
  • tags

If no attribute is selected, the app searches the list name by default.

To export or delete an Exception list, select the required action button on the appropriate list. Exception lists are exported to .ndjson format.

actions exception list

If a list is linked to any rules, you’ll see a warning appear that asks you to confirm the deletion. If no rules are linked to a list, it is deleted without confirmation.