Network Access Control (NAC) is a security solution that manages and restricts access to a computer network. It ensures that only authorized users and devices can connect, helping to protect sensitive data and resources. NAC systems evaluate the security posture of devices before granting access, checking for compliance with security policies. NAC can enforce policies based on various factors, such as user identity, device type, and location. By monitoring network activity, it can also detect and respond to potential threats in real-time. This proactive approach helps organizations maintain a secure network environment and reduce the risk of unauthorized access.