Hi .. You can easily restrict it if using version 7.X by using http inspection and defining a port-misuse command.
Please refer to the section about Instant messaging inspection on the admin guide for more details about the use of this command.
http://www.cisco.com/en/US/products/ps6120/products_configuration_guide_book09186a0080450278.html
The following is a briwf example
hostname(config)# http-map inbound_http
hostname(config-http-map)# port-misuse default action reset log
hostname(config-http-map)# port-misuse im drop
hostname(config-http-map)# exit
In this case, only the Instant Messenger application is denied. When HTTP traffic for the other
supported applications is received, the security appliance reset the connection and creates a syslog
entry
I hope it helps .. please rate if it does !!!
