A method is provided in which a network access system receives an initial request from a device requesting access to the network. In response to successfully authenticating the initial access request, the system causes a code to be transmitted in light emitted by one or more light fixtures within a physical space in which access to the network is to be restricted. The system receives information from the device requesting access to the network and determines whether to permit the device access to the network based on the initial request and on whether the received information is derived from the code transmitted by the one or more light fixtures, thereby indicating that the requesting device is within the physical space.