how can i block yahoo messenger through firewall.i had made a policy to blook port from 5000-6000 bec messanger use 5050 port.but it did not worked.the no op chat servers r too many so they cannot be blocked by ip add.i am using sun cobalt cube3 proxy and firewall. any ideas how it can be done

You can prevent users from installing it in the first place with a simple little command line utility. I found this info on computing.net. Open a DOS prompt. At C: prompt type CD Progra~1 and press return. Type COPY CON Yahoo! and press Return.Type Yahoo is now disabled and press return. Press CTRL and Z together and press return. You will see a message that 1 file was copied. You can prevent installation of MSN Messenger the same way. Just replace "Yahoo!" with "Messenger". they can download the program but during the installation process they get an error message that setup is unable to create the program directory. That is what this little piece of code does - it prevents the creation of the program's directory.