Port security is a network switch feature that controls which devices may connect to a specific physical port. The restriction is typically based on MAC addresses. If an unknown device is connected, the switch can shut down the port, drop the traffic, or trigger an alert. Port security prevents someone from simply plugging their own device into a network outlet and gaining access to the internal network. Combined with 802.1X and NAC, it creates a layered defense for network access. Configure port security especially in publicly accessible areas (conference rooms, reception areas).