Microsoft Security, Compliance, and Identity Fundamentals SC-900 Practice Question

Microsoft defines seven security layers in its defense-in-depth approach: physical, identity and access, perimeter, networking, compute, application, and data. Azure DDoS Protection and Azure Firewall are specifically cited as perimeter-layer controls that filter and block unwanted traffic entering the cloud environment. The physical layer protects datacenter facilities, the identity and access layer governs user and service authentication, and the data layer safeguards information at rest and in transit. Because only the perimeter layer focuses on controlling external traffic before it enters the internal network, it is the correct choice.