Optimize field filter performance using Splunk Web

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READ THIS FIRST: Should you deploy field filters in your organization?

Field filters are a powerful tool that can help many organizations protect their sensitive fields from prying eyes, but it might not be a good fit for everyone. If your organization runs Splunk Enterprise Security or if your users rely heavily on commands that field filters restricts by default (mpreview, mstats, tstats, typeahead, and walklex), do not use field filters in production until you have thoroughly planned how you will work around these restricted commands. See READ THIS: Restricted commands do not work in searches on any indexes if field filters are in use.

Overview

By default, a field filter configuration filters all events on the Splunk platform from all available hosts, sources, and source types in the specified target index, which can impact performance on unrelated search results. This section describes how you can improve performance by fine-tuning the index, hosts, sources, and source types that a field filter draws from. See Plan for field filters in your organization.

Prerequisites

To create, view, edit, and delete field filters, you must be a member of the admin or sc_admin role. Custom roles aren't supported for managing field filters.

Restrict field filters to specific indexes

You must specify the searchable target index when you set up your field filters.

Steps

To restrict a field filter to a specific index, follow these steps.

1. Select Settings and then Field filters from Users And Authentication.
2. Select New field filter.
3. In the Field filter and limit page, enter a name and optional description for your new field filter.
4. Enter the name of the target index you want to search that contains the data you want to protect. Only events from this index are filtered by the field filter.
   For example, to configure your field filter to filter events from an index called customers, set the target index to the customers index.
5. Enter additional information as needed to configure your field filter.
6. Select Next, and then select Next after reviewing the subsequent pages. Then select Save to update the field filter with your change.

Restrict field filters to specific hosts, sources, or source types

For more efficient searches and better performance, use the field filter limit settings in Splunk Web to restrict the field filters to a specific host, source, or source type. For example, your searches will be faster if you configure your field filter to filter events from a specific host called hostname1. Instead of filtering all events, only those events from the host hostname1 are filtered.

Keep the following considerations in mind when you plan to limit your field filter to a particular host, source, or source type:

• You can specify only one value for each field filter limit.
• The field filter limit settings do not support statements that include wildcards or the following operators: AND, OR.

Steps

This section describes how to use Splunk Web to edit an existing field filter to filter fields from specific hosts, sources, or source types.

1. Select Settings and then Field filters from Users And Authentication.
2. Select Edit from the Actions menu for the field filter you want to update.
3. In the Limit type field, select the host, source, or source type. Only one limit type is supported per field filter.
4. Enter the name of the host, source, or source type in Host limit, Source limit, or Source type limit.
5. Select Next, and then select Next after reviewing the subsequent pages. Then select Save to update the field filter with your change.

Examples

1. Set the source type for a field

Say you have a field filter that redacts values of the IP_addr field in searches with the string xxxx. The IP_addr field filter applies to all events with the IP_addr field.

To apply the IP_addr field filter only to events that have the IP_addr field and the cisco_syslog source type, edit the field filter by following these steps:

1. Select Settings and then Field filters from Users And Authentication.
2. Select the IP_addr field filter, then select Edit from the Actions menu.
3. In the Limit type field, select Source type.
4. In the Source type limit field, enter cisco_syslog.
5. Select Next and then Save.

See also

Protect PII, PHI, and other sensitive data with field filters

Create field filters using Splunk Web