Wireless keyboards are more convenient than standard wired models--after all, who doesn't want to get rid of another cord on their desk? But, as an unfortunate pair of wireless keyboard owners found out, the long range of some devices can make them a privacy and security risk.

A couple of neighbors in the Norwegian town of Stavenger both had new wireless keyboards from HP. These keyboards, like most other wireless models, transmit keypresses to the computer via radio signals that are beamed to a receiver. But the neighbors quickly discovered that if both of them used their PCs at the same time--even though they were more than a football field's length away from each other in different apartments--both receivers would output anything that either neighbor typed.

HP's product manager in Norway, Tore Särelind, was at a loss to explain the malfunction. "We have no logical or technical explanation for how this is possible," Särelind said. "The keyboard should have a theoretical radius of about 20 meters."

Radio experts say that local weather conditions, or even unshielded power cables, have the ability to amplify or increase the range of radio signals.

The incident highlights some of the risks associated with using radio frequency (RF) wireless keyboards. Many older models provide very limited security options--sometimes as few as 16 radio channels that you have to change by hand on both the keyboard and receiver. Newer RF keyboards can automatically switch between several thousand radio channels to ensure greater security--though even with these keyboards in place, a motivated hacker with the right equipment can receive whatever you type.

At home, RF keyboards might broadcast credit card numbers or important passwords. In a business environment, you could transmit salary information to the office gossip, or even send proprietary information to corporate spies.

Logitech representatives say their RF wireless keyboards scramble their security codes each time the computer boots up. With more than 4000 possible combinations in the Logitech models, it's unlikely (though still possible) that someone else's nearby receiver would pick up your radio signals. HP is increasing the number of security codes for its keyboards from 2 to 256.

RF keyboards that use the Bluetooth radio system provide the highest security. Bluetooth keyboards encrypt the radio signal, and synchronize with the receiver connected to the desktop when you start your PC. Even if the keyboard's transmission penetrates walls or crosses large distances, it can't be decrypted by any receiver other than the one that it's matched to. At press time, only Microsoft offers a Bluetooth-enabled wireless keyboard in the United States.

Other kinds of wireless keyboards, such as those operating with beams of infrared light, are practically immune to this kind of accidental transmission. As anyone who has ever used an infrared remote control for a TV can attest, not only will an infrared beam not penetrate walls, but even in the same room the signal sometimes won't get to its intended destination if you don't aim correctly.

The moral of the story: If you want to be absolutely certain of the privacy of anything you type, stick with a wired keyboard or try a Bluetooth model.

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