It’s not the first time boffins have proposed the use of smartphone accelerometers as an attack vector, but it’s scarily efficient: with as few as five guesses, Swarthmore College researchers say they can use phone moments to reveal user PINs.As noted in his paper (PDF - Practicality of Accelerometer Side Channels on Smartphones, lead author Dr Adam Aviv says phones' movements have been investigated as an attack vector before. Prior work has, however, used the phone’s gyroscope – or a combination of gyro and accelerometer – as the input sensor, and with relatively low accuracy (he cites a test that gave a worst case needing 81 guesses to arrive