The function of a network access control (NAC) system is to enforce security policies on devices attempting to connect to a network. NAC solutions monitor and authenticate devices, ensuring that only compliant and authorized devices gain access. This helps prevent unauthorized access and protects the network from potential threats. NAC can also segment networks to limit the spread of malware and enforce policies that require devices to have up-to-date security measures. Ultimately, it is a critical component of modern cybersecurity strategies, safeguarding sensitive data and resources.