A network apparatus which is detachable from a data processing apparatus and is mounted in the data processing apparatus to connect the data processing apparatus and a network installs an application and stores authentication information corresponding to the application in the storage of the network apparatus. The network apparatus acquires authentication information corresponding to the application from the storage of the network apparatus and the data processing apparatus in accordance with an application activation request. The network apparatus determines, on the basis of the acquired authentication information, whether to permit activation of the application.