Your network contains a server named Server1 that runs Windows Server 2008 R2. Server1 has the Streaming Media Services role installed.

You discover that anonymous users can access video content stored on Server1.

You need to ensure that user access to videos on the server requires authentication.

What should you do?

A.
From the Windows Media Services console, configure the Authorization properties.

B.
From the Windows Media Services console, configure the Authentication properties.

C.
From Internet Information Services (IIS) Manager, configure the Authentication settings.

D.
From Internet Information Services (IIS) Manager, configure the .Net Authorization Rules settings.

Explanation:
About authentication

Authentication is a fundamental aspect of security for a server running Windows Media Services. It confirms the identity of any user trying to access resources on your Windows Media server. Windows Media Services includes the following authentication plug-ins that you can enable to validate user credentials:
* WMS Anonymous User Authentication
* WMS Negotiate Authentication
* WMS Digest Authentication

Authentication plug-ins work in conjunction with authorization plug-ins: after users are authenticated, authorization plug-ins control access to content.
Windows Media Services authentication plug-ins fall into the following categories:

Anonymous authentication. These are plug-ins that do not exchange challenge and response information between the server and a player, such as the WMS Anonymous User Authentication plug-in.
Network authentication. These are plug-ins that validate users based on logon credentials, such as the WMS Negotiate Authentication plug-in.

When a user tries to access a server or publishing point, the server tries to authenticate users through an anonymous authentication plug-in. If more than one anonymous authentication plug-in is enabled, the server only uses the first one listed. If that attempt fails or an anonymous authentication plug-in is not enabled, the server tries to authenticate the user by using a network authentication plug-in. If more than one network authentication plug-in is enabled, the server tries to use the first one that is also supported by the client.

Source: http://technet.microsoft.com/en-us/library/cc754800.aspx