Network Access Control (NAC) is an approach to computer security attempting to unify endpoint security technology, user or system authentication and network security enforcement.
It uses a set of protocols to define and implement a policy that describes how to secure access to network nodes by devices when they initially attempt to access the network. NAC might integrate the automatic remediation process into the network systems, allowing the network infrastructure (such as routers, switches and firewalls) to work together with back office servers and end user computing equipment to ensure the information system is operating securely before interoperability is allowed.