A Side-channel Analysis of Sensor Multiplexing for Covert Channels and Application Profiling on Mobile Devices
This work exposes security vulnerabilities in mobile devices that could allow covert data exfiltration and application profiling, impacting user privacy and device security.
The paper demonstrates that Android's sensor multiplexing design, which shares the highest requested sampling frequency across applications, creates exploitable side-channels, enabling unprivileged malicious apps to establish reliable covert channels and profile other sensor-enabled apps.
Mobile devices often distribute measurements from physical sensors to multiple applications using software multiplexing. On Android devices, the highest requested sampling frequency is returned to all applications, even if others request measurements at lower frequencies. In this paper, we comprehensively demonstrate that this design choice exposes practically exploitable side-channels using frequency-key shifting. By carefully modulating sensor sampling frequencies in software, we show how unprivileged malicious applications can construct reliable spectral covert channels that bypass existing security mechanisms. Additionally, we present a novel variant that allows an unprivileged malicious application to profile other active, sensor-enabled applications at a coarse-grained level. Both methods do not impose any special assumptions beyond accessing standard mobile services available to developers. As such, our work reports side-channel vulnerabilities that exploit subtle yet insecure design choices in Android sensor stacks.