Some applications use dynamic ports and protocols, encryption, and other techniques to make the application traffic difficult to detect and manage. For these types of applications, there can be some limitations to the application behaviors that Application Control can manage.
One example of this type of evasive application is Skype, a popular peer-to-peer (P2P) network application. The Skype client uses a dynamic combination of ports that include outbound ports 80 and 443. Skype traffic is very difficult to detect and block because it is encrypted, and because the Skype client is able to bypass many network firewalls.
For information about how to block Skype, see Block User Logins to Skype.