In January 2006, Delaware County detectives traced images of child pornography found on the Internet to the address of a computer located at an Upper Darby home.

Shortly after they confiscated the suspect's computers for forensic examination, he fled.

When the detectives finally caught up with Walter Savage more than a year later, he was holed up in a room he had rented in a house in Yeadon - and he was back on a computer chasing his cyberspace fantasies.

But this time, Savage was using his neighbor's unprotected wireless signal. On his new computer, he had downloaded more than 100 images of child and adult pornography.

For law enforcement, tapping into wireless accounts is the latest way in which child pornography can evade the reach of the law.

"I think we are going to find more and more of it," said Delaware County Detective David Pfeifer, who is with the Internet Crimes Against Children (ICAC) task force.

Computer users, he said, do not often take the extra step to secure their wireless Internet routers, leaving their accounts vulnerable to Internet theft from outside the home.

Delaware County District Attorney G. Michael Green said there were more cases where child pornography was being downloaded by criminals using wireless service registered to another person. "That technique is a real concern," he said.

And it can also become a real problem for the unsuspecting wireless owner. The person who downloaded the pornography is gone, and it is the registered owner of the wireless account who is left to answer police questions.

Technically, "the account holder is responsible for the crime," said Detective Sgt. Gordon Samartino of the New Jersey State Police ICAC in Hamilton, where there have been a few cases involving the use of unprotected wireless to access child pornography.

"The search warrant ends up at that house," he said.

In apartment complexes or streets where houses are close together, it is easy for neighbors or drive-by cyberspace pilferers to pick up and use WiFi signals from unsecured wireless routers without paying for access.

"We view it the same as if you split into someone's cable line," said Mitch Bowling, a senior vice president at Comcast. "It is theft of services."

Bowling admits it is hard to find the offenders. Often, he said, "they are nomadic."

Comcast, he said, works to educate users to protect themselves: "We are not searching for the person driving through the neighborhoods."

A WiFi router that is not secured in one of two ways can be used by any computer within range - typically about 200 feet. One method is to encrypt the data stream that flows back and forth between the WiFi router and any computers within range. The other is to "authorize" the WiFi router to communicate only with specific computers.

In addition, security experts advise changing the default administrative password in the WiFi router; this will prevent hackers from reconfiguring the router surreptitiously, perhaps canceling the security settings.

Driving through a Springfield Township neighborhood in the county's gray Chevrolet Tahoe last week, Pfeifer was able to detect numerous open wireless accounts using a $60 handheld device the size of a pager. "Anybody can do it" with this device or a laptop with a wireless card, he said.

Last week, Pfeifer pulled up in front of a Springfield Township house. Within a matter of seconds, an Inquirer photographer accompanying him was able to download pictures of a singing Britney Spears onto his laptop, using an open wireless account from the house.

"That is four so far on this street," said Pfeifer, keeping track of how many open accounts he could track. "A lot of people are running wireless."

How far the wireless signal will go depends on whether it has to travel through walls of wood or concrete, said Brett Becker, a security analyst with the University of Kansas. It also has to do with the quality of the wireless card.

One signal Pfiefer picked up from the Delaware County Courthouse parking lot came from a law office across the street, about 50 to 60 feet away.

The lawyer, Eugene Bonner of Media, had no idea his wireless signal was unprotected or could carry that far from his office. "I'm calling my IT guy," he said.

Bonner's IT staff secured the signal that afternoon.

The act of hunting for an open wireless account to access is generally referred to as "wardriving." The name was derived from "wardialing," best known from the 1983 movie WarGames, starring Matthew Broderick as a teen who hacks into a military computer thinking it is a game.

Actually using an unprotected account is "piggybacking."

"Wardriving is like walking through a neighborhood and writing down the addresses," said Kevin Watkins, a researcher at McAfee, a computer security company. "Piggybacking is where it changes. Piggybacking is like entering the house."

It is not easy to detect someone piggybacking on your account, Watkins said. The service may be slower if the unauthorized user is downloading large files.

"Another way is if the feds knock on your door to see if the illegal activity is coming from your computer," Watkins said.

In December, Savage pleaded guilty to charges of possessing child pornography and received four years' probation. He was not found to be a sexually violent predator. As part of his sentence, he is allowed to use a computer only for work.

Pennsylvania law allows for probation in cases like Savage's; in other states, the penalties are more severe.

In January, an Idaho man was sentenced to 12 years in prison after police found 5,000 images and 180 videos on his computer.

Andrew Charles Tennant, 31, a dairy deliveryman, admitted he would wardrive to access the Internet from the dairies he delivered to and then view pornography in his car or employer's truck.

The Delaware County and Idaho cases focused on the crime of child pornography, not the crime of stealing wireless service. But get caught piggybacking in the United Kingdom and you could face up to five years in prison and a fine of about $1,900.

Another concern for those who try to police Internet crime is "hot spots," where anyone can anonymously use open wireless accounts, such as cyber cafes, hotel lobbies and libraries.

Rob D'Ovidio, an assistant professor at Drexel University, says such places are "a great haven" to launch criminal activity.

"Pornography is one of the many types of crimes where an unsecured network is the vulnerability," said D'Ovidio, who directs the university's computer crime and digital forensics research program.

Fraud, harassment, cyberstalking, identity theft, and downloading copyrighted goods are also crimes that can be committed anonymously using another's account, he said.