When a transparent authentication fails on the Web Security Appliance (WSA), the end user gets blocked access. This means that the user cannot access any web resources until they successfully authenticate. The WSA can use different methods to authenticate users transparently, such as Transparent User Identification (TUI), Transparent Identification, or Kerberos1. If none of these methods work, the WSA will send a block page to the user with a message explaining why the authentication failed and how to resolve the issue2. The block page can be customized by the administrator to provide more information or instructions to the user3.
References := 1: Implementing and Operating Cisco Security Core Technologies (SCOR) v1.0, Module 4:
Securing the Cloud, Lesson 4.3: Cloud Application Security, Topic 4.3.2: Cisco Umbrella, page 4-59. 2: User Guide for AsyncOS 12.5 for Cisco Web Security Appliances - GD (General Deployment), Chapter: Acquire End-User Credentials, Topic: Failed Authentication Credentials, page 4-67. 3: User Guide for AsyncOS 12.5 for Cisco Web Security Appliances - GD (General Deployment), Chapter: Customize End-User Notifications, Topic: Customize Block Pages, page 5-1.