Van Paschalis, seated, and The Learning Center consultant Nield Montgomery discuss security for computers that use a wireless connection to the Internet. Photo by Ralph Fountain.

To prove a point, Nield Montgomery, a consultant with The Learning Center, drove to work on a recent morning with his laptop computer's wireless modem on. He wanted to see if it could pick up signals from personal computers along the way.

During the 20-minute drive, Montgomery demonstrated how easy it is to electronically spy on computer data and communications using Wi-Fi. His laptop modem picked up signals from 150 Wi-Fi computer connections.

Wi-Fi is short for wireless fidelity and refers to wireless systems used to connect computers to the Internet. Many laptop computers have built-in wireless modems.

Manufacturers such as Linksys, a division of Cisco Systems, sell separate wireless devices that cost about $40 and let people wirelessly connect desktop computers to the Internet.

Using Wi-Fi is a way to avoid the hassle and expense of installing wires in a building or house, Montgomery said. But many Wi-Fi users are unwittingly and recklessly leaving their confidential data exposed to anyone with a similar Wi-Fi system.

Wi-Fi signals have become the 21st century version of the Wild West. Instead of bandits with revolvers, computer hackers inhabit this invisible territory.

Some spy on wireless computer users for fun. But others steal confidential information or vandalize databases.

In Montgomery's demonstration, many computer users' signals are identified only by numbers, which apparently came from the manufacturer. Among the named computer users were a taco shop, a real estate firm and an individual's proper name. To Montgomery, it was like flagging hackers and suggesting that they take a look at confidential information.

Of the 150 signals detected by Montgomery, only 40 were unprotected. In other words, anyone with a basic computer knowledge could have electronically eavesdropped on the computer users. They could even have gone into the computer users' databases and extracted confidential information, scrambled that information or made an unauthorized stock or bond trade using the computer user's identity.

AirDefense, a software company based in Alpharetta, Ga., explained the problem this way:

"Traditional wired networks use cables to transfer information, which are protected by the buildings that enclose them," the company said in a report. "On the other hand, wireless networks use the air, which is an uncontrolled medium. (Wireless) signals can travel through the walls, ceilings of buildings up to thousands of feet outside of the building walls. It is a shared medium that allows anyone in proximity to 'sniff' the traffic."

Many users don't bother to encrypt their Wi-Fi signals, Montgomery said.

It's easy for a teenage hacker to break into the private data contents of personal computers that are wirelessly connected to the Internet but have not been encrypted, said Van Paschalis, director of technical education at The Learning Center.

"It only takes about 15 minutes of very basic training to be able to do this," he said.

While security is important inside the homes and offices of wireless personal computer users, laptop computers and personal digital assistants may be even more exposed to hackers in coffee shops, airport lobbies, hotels and other Wi-Fi "hotspots," Montgomery said.

To provide minimal protection, a wireless computer user should follow computer equipment instructions for installing Wired Equivalent Privacy, which is a standard protocol for security.

WEP provides only minimal protection, similar to a tiny luggage lock, Montgomery said. However, it may be enough to discourage a data thief who can more easily access another totally unprotected, wireless system.

Montgomery urged every wireless computer user to take the minimal step of installing WEP.

"At least turn it on," Montgomery said. "Would you leave your house today and not lock your front door?"

Many businesses, ranging from casinos to banks and insurance agencies, need more than the bare minimum in security.

They may be required to protect sensitive information under the Health Insurance Portability and Accountability Act of 1996, which protects the privacy of patients' health records, or federal laws governing financial information.