On the Feasibility of Detecting Non-Cooperative Wi-Fi Devices via a Single Wi-Fi-Router

Detecting intruding devices using Wi-Fi based indoor positioning systems running on commodity Access Points (APs) makes demands on both compatibility with available hardware as well as not depending on the intruding device to cooperate with the system. In this paper, we examine the feasibility of detecting non-cooperative Wi-Fi devices with a single AP reliably and whether available hardware in affected homes is sufficient in carrying out the task. Commonly, indoor positioning systems require non-trivial setups with specifically tailored hard- and software, as the aspiration is to maximize precision for which the devices to be located will actively assist, which we cannot rely upon. First, criteria are derived that help identify indoor positioning systems suitable in our use case, specifically Channel State Information (CSI)-based approaches. These systems are then evaluated on both compatibility with commodity hardware and accuracy by conducting experiments on available devices. We show that despite promising premises the commodity hardware landscape is insufficiently supporting such a system for widespread use and that the one compatible router we found can not detect an intruding Wi-Fi device accurately enough even in favourable conditions.