Blocking Music Sharing.

["Johnson, Mark" <mjohnson () nmcr com>]

Due to the legal issues, I am trying to block access to sites like Kazaa
and Limewire in the office.  If I am not mistaken, these networks can
use different ports each time, so there is no way to block it at the
firewall.  Is this right?  And if so, what is the best way to block
access to these types of sites?
 
Many thanks,
Mark J.