The rise of keyloggers on smartphones: A survey and insight into motion-based tap inference attacks

Smartphone sensing capabilities have opened new opportunities for innovative User Interface (UI) and context-aware applications. They have also opened new possibilities for potential risks to user privacy and security infiltration. Researchers have recently explored a new attack vector that exploits the built-in motion sensors to infer user taps on smartphone touchscreens. This new side channel has introduced the threat of keylogging to smartphones despite the lack of physical keyboards. In this paper, we review this type of attack and survey the leading works in the literature to highlight the underpinning motivations and threat model. We also discuss the main issues in the design and implementation of the new attack, in order to provide insights into the practicality, prospects, and limitations of the different approaches. Different countermeasures that can mitigate the rising threat are investigated, and recommendations for further research on this emerging trend are discussed. A comparative summary of the surveyed works is also presented.