Failed to Block Facebook Chat Consistently
Step 1. Enable decryption.
For more information about Decryption, please refer to "How to Implement and Test SSL Decryption".
Step 2. Configure your security rule to block "facebook-chat" and "facebook-mail" applications.
Step 3. Create another security rule that allows "facebook-base" application. Add this security rule below the rule created in Step 2 above.
With the above configuration, the user still can browse to Facebook, but will not be able to use Facebook-Chat.