Compromising Electromagnetic Emanations of USB Mass Storage Devices

Universal Serial Bus (USB) has become the dominant Plug & Play interface for personal computers and continues to grow. Any digital communication source emits secondary or unwanted emissions, called compromising emanations, as they can be received and used to reconstruct the original transmitted information, thereby compromising the transmitted messages. This paper presents a number of experimental results regarding the USB communication between a personal computer and a USB memory device (USB bulk transfer) that has been performed in a specialized laboratory, and illustrates the capability of restoring information transmitted at bit level only from receiving the compromising radiation emitted by this communications bus. Comparative results for a shielded and unshielded device will also be illustrated. Finally, some TEMPEST protection methods are identified and presented against leakage of information through the compromising radiation of USB communication.