Network Access Control (NAC)

Network Access Control solutions evaluate the security posture of devices before allowing them onto the network. When a device attempts to connect, the NAC system checks factors such as the device's identity, operating system patch level, antivirus status, configuration compliance, and user authentication credentials. Devices that fail these checks can be denied access, placed in a quarantine VLAN for remediation, or granted limited access.

NAC operates through several mechanisms, including IEEE 802.1X port-based authentication, RADIUS server integration, and agent-based or agentless endpoint assessment. Pre-admission NAC evaluates devices before granting network access, while post-admission NAC continuously monitors connected devices and can revoke access if compliance lapses.

Implementing NAC is particularly important in environments with bring-your-own-device (BYOD) policies, IoT devices, guest networks, and contractor access. Effective NAC deployment requires integration with existing directory services, clear policy definitions for different device types and user roles, graceful handling of non-compliant devices, and comprehensive logging. NAC complements other security controls like network segmentation and endpoint security to create a robust defense-in-depth posture.