What does an IAS server leverage for user validation?

The correct answer pertains to how an IAS (Internet Authentication Service) server uses the COMPOSE Domain's Active Directory for user validation. Active Directory is a directory service developed by Microsoft that provides a variety of network services, including user authentication, authorization, and management of directory objects.

When an IAS server is configured to leverage Active Directory, it integrates seamlessly with a network's infrastructure, allowing for centralized user account management and easier scalability. By utilizing Active Directory for validation, the IAS server is able to authenticate users based on the credentials stored within the domain, ensuring a secure and streamlined process. This is particularly useful in enterprise environments where user credentials need to be managed efficiently across multiple services and applications.

In contrast, a local database would imply that user credentials are stored and managed on the server itself, which can limit scalability and complicate user management in larger networks. An external authentication server might provide alternative ways of verifying identities, but it doesn't necessarily leverage the existing infrastructure provided by Active Directory which is integrated into the network. Similarly, cloud-based identity management solutions may be effective but do not typically align with the setup of utilizing a local domain's Active Directory for user validation.