I Can See What You Are Seeing: A Trial of Intercepting Display Image Using Electromagnetic Emanations from VGA Cable

Wu Jinzhou

VGA cable and display unit are typical mediums for information transmission and output in
a computer system. Since VGA cable is made by metal wires and carries display signal, it
eventually emits electromagnetic waves. These emanations reveal display image and may
cause private and sensitive information leakage. This report describes the experiments and
analysis of the interception of personal computer’s display image using emanation of
electromagnetic wave form VGA cable. In the experiment, a modern full HD flat LCD
screen connected to a personal computer via VGA cable is used as the target display, the
interception is performed under normal office/home environment condition. In our work, we
have (1) studied the computer display monitor timing and identified the sync information,
(2) intercept the electromagnetic emanations from VGA cable, (3) processed the intercepted
data and restored the display image on the target screen and (4) analyzed the image
reconstruction results by repeating step (2) at various distance. We have fully or partially
restored the display image at the distance form less than 1 cm up to 30 cm away form the
signal source. Both observation results and analysis results suggest that the bright text on
the dark background is more secure than the dark text on the bright background in against of
interception under experimental settings.

I Can See What You Are Seeing A Trial of Intercepting Display Image