SAN DIEGO -- Do you have wireless Internet? If you do, you've also got a potential security problem on your hands.

Hackers can intercept your signals while going past your home, your office and anywhere else you can take a laptop, or a hand-held computer. What they can do with those signals could ruin your life and many others.

There are millions of hackers who can break into a wireless computer or even a Palm Pilot or Blackberry. They are called drive-by hackers, and they gain access by picking up the wireless broadcasts from some distance away.

They like to get in their cars and go "war driving," as they call it. Most don't misuse the data they find, but there are plenty of hackers out there who could do incredible harm.

To see how it is done, television station KNSD sent a reporter war driving with San Diego computer security consultant George Spillman.

"I'm going to start scanning here as we're driving down the road, and it's going to start naming off the (access points) as we pick them up," Spillman said.

After 15 minutes of war driving past shopping centers, apartment complexes and suburban neighborhood, Spillman logged hundreds of access points, or APs, for wireless networks. Too many are open doors for signal-stealing hackers who can learn your passwords, read your e-mail, use your credit card numbers and turn your home computer system into a weapon, the station reported.

"They could be loading spam. They could be loading viruses on the Internet," Spillman said. "You could have child pornographers using your system. You could have terrorists driving by your house, using your system to send a message. And the only traceable route back to it is you. It stops at your house."

Hackers don't need exotic equipment to do this. All they need is a laptop computer with a consumer wireless card.

"We took this one apart and soldered in an external connection so we can use it with a secondary antenna," Spillman said.

Serious hackers use equipment to enhance the signals. And they can get all the technology they need right off the shelf at your local mall.

Many of the wireless networks being sold to consumers offer security measures to keep hackers out. But the hackers look for countermeasures, and the good ones find them.

Experts say you can make your system harder to hijack by taking basic precautions with your wireless network:

• Encrypt
• Change passwords frequently
• When you're gone or asleep, shut everything down

If you don't feel like that is enough, a company called Downtown IT will go to your home or business and secure your system for you. Get more information at the company's Web site.