Which of the following is NOT a security concept for customers of cloud computing?

The selection of physical security as the correct answer is based on the understanding of responsibilities in cloud computing environments. In cloud computing, the provider typically handles physical security measures, such as securing the data centers, ensuring only authorized personnel can access the hardware, and protecting the physical infrastructure from threats such as natural disasters or theft.

Customers of cloud services are generally responsible for securing their data, applications, and access controls. In contrast, network security, access control, and cryptography are key concepts that directly pertain to the responsibilities of cloud customers. They must implement strong network security measures to protect their data in transit, manage access control to applications and data, and employ cryptographic techniques to secure sensitive information.

Thus, understanding the division of responsibilities in cloud computing environments clarifies why physical security does not fall under the direct purview of cloud customers.