Specify whether to authenticate users through Internal Authentication (application) only, or through External or Internal Authentication depending on the individual user setting.
Set it as INTERNAL (default) to allow user authentication only through the application.
Set it as DEPENDS_ON_USER_SETTING to allow external authentication or to allow authentication based on the Authentication Method selected for the user.
You can use the User form (on page 1) to specify the Authentication Method for each user.
See also: FRMSECURITY024 (USER_AUTHENTICATION_METHOD_DEFAULT) (on page 1), FRMSECURITY025 (EXTERNAL_AUTHENTICATION_PROVIDERS_CONFIG_XML) (on page 1).
Since the FRMSECURITY023, FRMSECURITY024, and FRMSECURITY025 settings are GLOBAL settings, the Override button is enabled only when you select the Global scope level in the left pane in the Edit Configuration form (on page 1), as shown below: