What if someone just around the corner could see what you’re looking at on your computer screen without a physical or wireless connection and without even being in your system? Sounds like fiction, and it sounds scary. But it’s based in reality, and it’s been around for a long time.

Not to fear (I think), because the NSA has been on the case. The process I’m talking about is called Van Eck phreaking. Ever heard of it? Not many people have. Van Eck phreaking is the detection of electromagnetic emissions to spy on what is displayed on a CRT (cathode ray tube) or LCD (liquid-crystal display) monitor as well as the inputs coming from a computer keyboard. In 1995, Wilm van Eck published a paper and the first proof of concept on the idea. He even explained that it could be done from a large distance.

What makes Van Eck phreaking so scary is that it is untraceable. Intrusions are usually done through a computer network, making detection or the ability to trace the action possible. With Van Eck phreaking that is impossible. The electromagnetic radiation that is emitted from a computer monitor and the cord linking the monitor, or even the keyboard and its cord, can be picked up by an antenna array and displayed on another monitor. All of the information that is on the screen will be displayed as the user sees it, and no one would even know its happening.

The NSA has a codename for this type of spying called TEMPEST. TEMPEST includes information and methods on how to spy on others as well as countermeasures to protect a computer system against this spying. The NSA’s methods are of course classified on how to do this type of spying, but the standards for protecting oneself against this spying are well known and have been released. Not only does TEMPEST address spying dealing with electromagnetic radiation, but it also addresses spying through mechanical vibrations or sounds.

NSA Headquarters

Even though this sounds terrible that someone could be spying on you looking at that fuzzy, cute cat picture, I would bet its not something to worry about. But corporations and government entities have a real threat from this type of intrusion. Many companies, as well as the government, take this threat seriously and have countermeasures in place. One way they counter a possible attempt is by shielding electromagnetic emission with other metals, or encasing a room with metal walls. Another countermeasure involves scrambling the video signal so that the signal is much harder to be reproduced. See? There really isn’t anything to worry about.

But hold on. Research completed in 2004 about the risk of eavesdropping on the electromagnetic signals from flat-panel displays and laptops found that they were susceptible and the ability to spy on them could be done with equipment that cost less than $2000. Let’s hope this doesn’t catch on.

Check out this news report video that shows how Van Eck phreaking is done, how clear the image is, and how a password can be stolen. Good fun.