Blocking MSN Messenger traffic by using HTTP filtering in ISA

FYI: Tom Shinder at www.isaserver.org has published a nice little step-by-step guide to blocking MSN Messenger traffic in ISA with the short name - ISA Firewall Quick Tip: Blocking MSN Messenger Access through the ISA Firewall while Enabling Access to Some Users.

In this article we'll go over the following procedures: Create the HTTP/HTTPS Access Rule to Deny Access to MSN Messenger; Configure the User Group Exception and the HTTP Security Filter on the Deny Rule; Create the Allow Rule for the Excepted Users.