All it took was a $500 telescope trained on a reflective object in front of the monitor. For example, a teapot yielded readable images of 12 point Word documents from a distance of 5 meters (16 feet). From 10 meters, they were able to read 18 point fonts. With a $27,500 Dobson telescope, they could get the same quality of images at 30 meters.
Backes has demonstrated his work for unnamed government agencies. "It was convincing to these people," he said. Spheres work great, he said. Spoons and eyeglasses, which are curved but not spherical, less so. So you can imagine "these people" sneaking teapots next to targets' PCs.
"If you place a sphere close by, you will always see the monitor," he said. "This helps; you don't have to be lucky."
But actually image analysis algorithms may eventually enable spies to get readable images off of walls and even the human eye. They've looked at white walls two meters from the monitor and picked up readable images.
Unfortunately for the NSA, there is an easy defense. "Closing your curtains is maybe the best thing you can do," Backes said.
Also, at UC Santa Barbara, they're analyzing video of people's hands typing and guessing right about 40 percent of the time.