How to block Yahoo Messenger WITHIN Yahoo Email

btm02sf used Ask the Experts™
I was able to successfully block a variety of instant messenger applications thruogh a combination of GPOs and blocked domain sites for a client of mine. They use Windows 2003 Small Business Edition and a Netgear Rangemax Wireless Gigabit Router WNR3500 (one of the latest models).
Unfortunately, I couldn't figure out how to block the Yahoo messenger within the Yahoo email site, without blocking complete access to Yahoo email (blocking TCP port 443 will block acccess to Yahoo email)
I've done extensive research for the past few days, and I just couldn't find a solution to this problem.
Any help would be really appreciated. Thank you so much.
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Actually, 443 is SSL, so blocking that will disable more than just yahoo webmail - it should disable anything that requires a secure/https connection.

Most chat programs like ICQ/AIM/yahoo messenger are becoming semi-intelligent, such that if their regular ports are blocked they try other ports... and in yahoo messenger's case one of the ports it tries is 80. You won't get much done if you block port 80, obviously. One way might be to block incoming connections from the whole IP range (looks like yahoo owns /22)... that should stop anyone else from starting a chat session with them.

Doesn't using the messenger button on actually start the messenger program locally, though?
If there's no way to stop that from starting (or stop it from being installed) with a GP, you could try something like TerminatorX (, which isn't free, but they do offer site licenses.


Thank you so much for your help. I will suggest to my client the purchase of Terminator.

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