Detecting Wireless Spy Cameras Via Stimulating and Probing

The rapid proliferation of wireless video cameras has raised serious privacy concerns. In this paper, we propose a stimulating-and-probing approach to detecting wireless spy cameras. The core idea is to actively alter the light condition of a private space to manipulate the spy camera's video scene, and then investigates the responsive variations of a packet flow to determine if it is produced by a wireless camera. Following this approach, we develop Blink and Flicker -- two practical systems for detecting wireless spy cameras. Blink is a lightweight app that can be deployed on off-the-shelf mobile devices. It asks the user to turn on/off the light of her private space, and then uses the light sensor and the wireless radio of the mobile device to identify the response of wireless cameras. Flicker is a robust and automated system that augments Blink to detect wireless cameras in both live and offline streaming modes. Flicker employs a cheap and portable circuit, which harnesses daily used LEDs to stimulate wireless cameras using human-invisible flickering. The time series of stimuli is further encoded using FEC to combat ambient light and uncontrollable packet flow variations that may degrade detection performance. Extensive experiments show that Blink and Flicker can accurately detect wireless cameras under a wide range of network and environmental conditions.