The risk-based authentication (RBA) message policy defines the message that users see when they are prompted to configure an identity confirmation method. When you delete this policy, it is removed from the deployment. If you delete a policy that is assigned to a security domain, the deployment default policy is automatically assigned to the security domain.
In the Security Console, click Authentication > Policies > RBA Message Policies > Manage Existing.
Use the search fields to find the policy that you want to delete.