4dfda130_Network_Security__Description_and_exceptions
IM, chat, skype The entire Internet. [Description and exceptions] 
Instant messaging, chat, and internet telephony programs such as AIM, iChat, Windows Messenger, IRC, and Skype work through the firewall. Users are clients who login to servers; servers relay messages between users. Since the user initiates the original outbound login connection to the server, the firewall allows the connection. An attempt to run your own IRC or other chat server will be blocked by the firewall.
Network Security
Description and exceptions