It's Possible To 'Steal' Data By Manipulating Screen Brightness

© Ben-Gurion University of the Negev/Engadget   Researchers figured out a way to steal information from an isolated computer not connected to the internet. It has to do with manipulating screen brightness.

By Courtney Linder, Popular Mechanics

• Researchers from Ben-Gurion University of the Negev in Israel have figured out a way to steal information from an isolated computer not connected to the internet.

• By taking advantage of small changes in color and brightness on LCD monitors, bad actors could use cameras to "see through" the ordinary screen's content, revealing vulnerable data.

• Although this kind of attack would be complicated to pull off, it's an example of ways that researchers are trying to stay one step ahead of the hackers.

Hackers know some insidious ways to siphon data, so scientists have to think up as many scenarios as possible to keep abreast of the bad actors. Mordechai Guri, head of research and development for the Advanced Cyber-Security Research Lab at Ben-Gurion University of the Negev in Israel, is on the case.

Guri figured out that by exploiting small changes to the RGB values in a PC's liquid crystal display—RGB being a color model used in computing to create a wide range of tones from just red, green, and blue—it's possible to pull information from someone else's screen, even if the computer is "air-gapped" and not connected to the internet. In other words, changes to the computer screen's brightness can create vulnerabilities that hackers can take advantage of with some effort.

"In the proposed modulation, the RGB color component of each pixel is slightly changed," Guri explains in a new scientific paper published to the preprint server arXiv. "These changes are invisible, since they are relatively small and occur fast, up to the screen refresh rate."

Here's what's going on: As the pixels change color, a small portion of each voxel is altered. So for instance, a pixel that's ordinarily pinkish can be changed ever-so-slightly to a more red hue. This is all done through an "image brightness encoder," which modifies the brightness of the pixels according to each bit (labeled in binary code with a "1" or "0").

"The small changes in the brightness are invisible to humans but can be recovered from video streams taken by cameras such as a local security camera, smartphone camera or a webcam," Guri says.

© Ben-Gurion University of the Negev   How to Hack Data by Manipulating Screen Brightness

Using recording devices to both access and capture imperceptible data is called display-to-camera communication. It's a class of hacking that doesn't really require a computer to be connected to the internet—and in this case, that's exactly the kind of limitation that the researchers wanted to explore. All that's needed is surveillance equipment pointed at a computer screen infected with malware.

Specifically, malware installed on a compromised computer can modulate sensitive information like encryption keys or passwords inside the brightness of the screen, Guri explains. So this is quite a dangerous hack, as it can all happen right beneath the computer user's nose.

To be fair, this looks pretty damn difficult to pull off. Who leaves a security camera pointed at a computer that's intentionally disconnected from the internet for data safety reasons? And hey, good luck installing malware on that computer—you'll need to physically infect the device, like through a USB stick, since it's not connected to the internet.

Still. Pretty sinister stuff!