What aspect does NAC primarily focus on?

Network Access Control (NAC) primarily focuses on restricting access to the network for unauthorized users. This is essential for maintaining the security and integrity of a network. NAC systems enforce policies that determine which devices or users can access network resources, based on various criteria, such as the user's identity, device compliance, and the security posture of the device attempting to connect. By ensuring that only authorized users and compliant devices are allowed onto the network, NAC minimizes the risk of security breaches, data leaks, and malware infections.

The other aspects mentioned, while important in their own right, do not align with the primary focus of NAC. Increasing bandwidth pertains to enhancing network performance, identifying potential threats is more related to intrusion detection systems, and backing up critical data is a crucial part of data management and disaster recovery, rather than access control. Thus, NAC's core functionality is centered on controlling who and what can connect to the network, underscoring the importance of security in access management.