When developing Metro style apps, Network Isolation helps your product to take advantage of the isolation mechanisms that will keep the app and system secure.
The new Windows Runtime APIs enable a developer to control the security profile of an app under development. Network access is part of this application security model. Not all apps will require access to the network. However for those that do, Windows provides the appropriate level of granularity for apps to access the network securely.
With network isolation, developers can define the scope of the network access required for each process, which prevents a process without the appropriate scope from accessing the specified type of network or connection. The ability to set and enforce these boundaries ensures that compromised apps have access only to networks they have explicitly been granted access to, significantly reducing the scope of their impact in other apps or the system itself.
Download and Read more about Network Isolation for Metro style Apps http://www.microsoft.com/download/en/details.aspx?id=27534. This paper provides information about network isolation for Windows operating systems. It provides guidelines for developers to determine the network boundary that a Metro style app will operate in, and what capabilities will be necessary to access required resources.