#4 Private Components
In the past, all components configured in a COM+ Application were intrinsically public. In other words, by configuring the components, they were able to be called by anyone who had the authorization to do so (assuming COM+ security was configured). In Windows .NET Server, the Activation tab of the component includes the "Mark component private to application" check box, which allows a developer to ensure that the component is only accessible from other components in this application.
This feature comes in very handy when you have built components that are meant to not ever be called from a base client; for example, components that log statistics about a transaction invoked from a base client.