Pre-process rules

Create pre-process rules to perform actions on incidents as soon as they are ingested.

Pre-process rules enable you to perform certain actions on incidents as soon as they are ingested (after classification and mapping) but before the incident is created in Cortex XSOAR. These rules enable you to drop, deduplicate, link, or close incoming incidents based on specific criteria. For example link the incoming incident to an existing incident, or under preconfigured conditions, drop the incoming incident altogether.

When creating pre-process rules you can test them on existing incidents to see how they perform.

Creating a pre-process rule consists of a three-part process using the preprocess wizard.

1. Select the incident field and value you want the rule to apply.
2. Select the action to perform on the incident, such as link and drop.
3. Add the criteria to compare existing incidents with the new incident, including the time range and oldest and newest incidents.

After you create a rule in the Pre-Process Rules tab, you can do the following:

• View, edit, copy, or delete the pre-process rule.
• Enable/disable the pre-process rule.

Rules are executed in the order they appear (from top to bottom). You can drag and drop rules as required. Only one rule is applied per incident.

Rule actions for pre-process rules

The following table describes the rule action for pre-process rules.

Option	Description
Link and close	Creates an entry in the Linked Incidents table of the existing incident to which you link, and closes the incoming incident. If an existing incident matching the defined criteria is not found, an incident is created for the incoming event.
Close	Closes the incoming incident. The incident will be created, but the associated playbook doesn't run.
Drop	Drops the incoming incident and no incident is created. Used for incidents that have low severity, no severity, or they have no value and don't need to be investigated.
Drop and update	Drops the incoming event, and updates the Dropped Duplicate Incidents table of the existing incident that you define. In addition, a War Room entry is created. If an existing incident matching the defined criteria is not found, an incident is created for the incoming event.
Link	Creates an entry in the Linked Incidents table of the existing incident to which you link.
Run a script	Select a script to run on the incoming incident. Note Pre-Process rules that use system-based scripts such as GetIncidentsByQuery, by default, are run according to the defined role (Limited User). For example, if the GetIncidentsByQuery script runs with the Limited User role, it also runs with the Limited User role in the Pre-Process rule. You can change the default by either detaching the script and updating the RunAs field such as DbotRole, or create a wrapper script with the required role set in the RunAs field. The wrapper script calls the system-based script. The system-based when called by the wrapper script runs with the role assigned to the wrapper script. Pre-processing scripts can access sensitive incident data. As best practice, we recommend assigning a Role for the pre-processing script to allow only trusted users to edit it.

Create a pre-process rule

Create a pre-process rule

Pre-processing rules enable you to perform certain actions on incidents as they are ingested into Cortex XSOAR. You can, for example, link an incoming incident to an existing incident, or under certain conditions, drop the incoming incident altogether.

Before you begin, search for incidents that you want the pre-process rule to apply and click Investigate, so that those incidents are available for testing.

1. Select Settings & Info → Settings → Object Setup → Incidents → Pre-Process Rules → New Rule.
2. In the Rule Name field, type a name for the rule.

   Give a meaningful name that helps you identify what the rule does. This will be useful when viewing the list of rules.
3. In step 1 Conditions for Incoming incident to apply the rule for incidents, do the following:

   1. Select a field and value.

      For example, if you want to apply the rule to a phishing incident type:

      Field	Filter	Value
      Type	Equals (String) Note For more information about filters, see Filter considerations, categories, and built-in filters.	Phishing

   2. Add an AND statement to your filter, if required.

      For example, if you are running a phishing awareness campaign, add Email Subject and in the value field, type the relevant text.
   3. If you want an OR statement, click the + sign.

      For example, you may want the rule to apply to blocked or spam alerts.

      Note

      If you want to remove an ADD or OR statement, click the - sign.
4. In step 2 Action, select the action to take if the incoming incident matches the rule.
5. If relevant, complete section 3.

   This section enables you to link or update an incoming event and drop or update the incident depending on the selected criteria.

   Section	Options
   Link to	Relevant when selecting Link and close and Link Determine if you want to link to the oldest or newest incident. Select the time range Select if you want to search for closed incidents. Select the incident field and value you want to link. For example, if you want to link the Email Subject field of the existing incident to the new incident, do the following: Field: Email Subject Filter: Is identical (Incoming incident) Value: to incoming incident (this field is prepopulated)
   Update	Relevant when selecting Drop and update Drops the incoming event and updates the incident defined: Determine if you want to link to the oldest or newest incident. Select the time range Select if you want to search for closed incidents. Select the incident field and value you want to drop and update.
   Script	Choose a script From the dropdown list, select the script to run on the incoming incident. Only scripts that were tagged preProcessing appear in the drop-down list.

6. (Optional) In a remote repository environment, you can view the relevant dependencies to ensure that all necessary dependencies are propagated or pushed to the remote repository.
7. (Optional) To check that the rules, click Test.

   Testing is useful to check that you are receiving the desired results before putting a rule into production. We recommend you fetch data from an existing incident as a sample incident against which the rule can run. You can also manually enter JSON to use as a test sample or edit the JSON from an existing incident using the Edit button.
8. Save the rule.

Pre-process rules examples

Drop incidents

When you run a phishing awareness campaign and send training emails to your employees, you want your employees to report the emails but you don't want to investigate. In this example, we create a condition for incoming incidents with the email subject You've Won the Best Employee Award, and drop those incidents without linking them to another incident.

preProcessing-8.png

Drop and update incidents

In this example, you want a pre-process rule to do the following:

• Apply to incidents that are ingested from the Sample Incident Generator.
• Drop incoming events and update the incident, if the name of the existing incident is identical to the incoming incident.

  You can add multiple conditionals to check for duplicates (not just the incident name) such as a Threat ID, incident ID, email, and host.

1. Create a pre-process rule.

   

   pre-process_rule.png
2. (Optional) Test the rule to ensure that it is working correctly.

   

   pre-process-test.png
3. (Optional) Go to an incident and check the Context Data (Side panels).

   Review the droppedCount key (line 52).

   

   pre-process-context.png

Drop incidents and drop and update existing incidents

Watch the following video to see how to drop blocked or spam incidents and drop and update existing incidents: Preprocessing.