by Michael LeMay, Jack Tan
Computer equipment produces a wide range of emanations in the visible, electromagnetic, and acoustic spectra. It is well known that electromagnetic emanations can reveal information about the operations being performed by a machine, and it has recently been shown that acoustic emanations can do the same. Additionally, techniques have been developed to manipulate electromagnetic emanations so that they surreptitiously transmit data to a remote receiver. In this paper, we similarly demonstrate how acoustic emanations can be manipulated to transmit arbitrary data and show how this technique can be used to create a practical, software-only acoustic keylogger. Finally, we recommend countermeasures to prevent such an attack from being performed.