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Re: howto block yahoo messenger

> I still fail to understand how blocking http://pager.yahoo.com would
> the Messenger service from working 'cos that server is a mere http server
> thats all. Messenger doesn't use it to connect to its database or nething.
> And though Messenger uses port:80 like u said......it also needs port 5050
> to effectively "send-messages" across the service.
> Something else that this brings up: Even if u do block the port the user
> still configure the service to run on some other port (well not in this
> particular case but on a more general basis).
if you block all access but http access thru a proxy server, then yahoo
messenger does http tunneling, using the http server at pager.yahoo.com. so
if u disable access to all the other ports (or if u don't hav a nat or
direct net conn) and disable pager.yahoo.com from the proxy server (which
can be squid, ms isa server, ms proxy server, etc..) then u can effectively
stop yahoo messenger. as the host field in the http headers is

if yahoo is not using http tunneling, then it can be using socks proxy, or
it can do a direct conn over a nat (or if the comp has a valid ip address
connected to the net) then yahoo can use any port, so port blocking does not
work with yahoo messenger.

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