The similar questions have been asked a lot in this newsgroup. Windows
Media Services itself are unable to perform advanced authorization required
for some applications like the one you have.
There are third-party solutions supplementing Windows Media Services. This
the help of that software it is possible to perform advanced users
authorization based on HTTP referrer, IP address or unique user ID.
http://voynex.com/wmsbilling is the example of such a product.

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Regards, Vladimir
http://voynex.com - custom software development, solutions for digital media
(pay per view, billing, protection, access control)
> Hi, i have a server that is running WMS 9 and is used for streaming live
> content. I have built an application that has an embedded media player in it
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> to protect the stream? I thought of dynamically controlling the IP list but i
> cannot find a way to do that.Any ideas? Thank you.