Description
This page demonstrates how magnetometer on mobile devices can be disturbed by the CPU. A distinct CPU pattern is produced by alternating between high (up to 100% CPU) and idle CPU loads lasting 2 seconds each (see example below). At the same time, magnetometer is recorded using the Generic Sensor API. After ~40 seconds, sensor measurements are shown along 3 axes. On many smartphones, the pattern is visually distinguished in the sensor measurements.
Potential privacy implications are discussed in the MagneticSpy paper.
CPU activity pattern
Example: sensor measurements recorded on a Google Pixel 2
