Analyzing and Defending GhostTouch Attack Against Capacitive Touchscreens

Capacitive touchscreens have become the primary human-machine interface for personal devices such as smartphones and tablets. In this article, we present GhostTouch, the first active contactless attack against capacitive touchscreens. GhostTouch uses electromagnetic interference (EMI) to inject fake touch points into a touchscreen without the requirement to physically touch it. By tuning the parameters of the electromagnetic signal and adjusting the antenna, we can inject two types of basic touch events, taps and swipes, into targeted locations of the touchscreen and control them to manipulate the underlying device. We successfully launch theGhostTouch attacks on nine smartphone models. We can inject targeted taps continuously with a standard deviation of as low as $14.6 \times 19.2$ pixels from the target area, and a distance of up to $\text{40}\; {\text mm}$. We show the real-world impact of the GhostTouch attacks in a few proof-of-concept scenarios, including pressing the button, answering an eavesdropping phone call, and swiping up to unlock. Finally, we propose touchscreen reinforcement and attack detection mechanisms to mitigate the threat of GhostTouch attack.