All computer screens emit electromagnetic waves that can be intercepted by criminals who then use the data to reconstruct what is displayed. Research on the topic is largely classified. But it’s not a secret that even distances of 100 meters and more between the attacker and the target PC can still be critical, depending on the equipment used and the surrounding area (walls, large objects, trees etc.)

The phenomenon, which is known as Tempest, was first publicly researched on in the 1980s but still poses a problem to IT security. Now Japan’s Nippon Telegraph and Telephone (NTT) showcased a device the size of a mobile phone, which they say is effective against emanations.

The Tempest market offers software, metallic tents, shielded computer hardware to prevent data theft. Aiming institutions such as police, secret services, banks and the military, vendors often charge up to six-digit sums and more for their products. However, NTT’s invention just plugs into the PC and superimposes electromagnetic waves on top of signals emitted from screens to block compromising emanations.

NTT’s promises its device will cost less than $1,000 and will be sold starting in autum.