PORTSMOUTH — One day last August, the Secret Service paid a visit to the new owners of Custom House Coffee off West Main Road.

The news they brought was bad: Computer hackers, whereabouts unknown, had used sophisticated spy software to break into the store’s wireless network and steal the credit and debit card numbers of customers.

In all, about 50 customers of Custom House Coffee had been victimized, as early as May 2008, according to Police Chief Lance Hebert. But it wasn’t until the victims got their bank or credit card statements and saw charges they didn’t recognize that they realized they had been robbed. As the police reports started to filter in, detectives began connecting the dots.

So far, the thieves have run up nearly $50,000 in unauthorized charges on the victims’ cards in eight states, said Herbert, whose department just recently confirmed that the crimes occurred. The victims, however, have all been made whole by their card companies.

Identity theft is nothing new, says Assistant U.S. Attorney Lee Vilker, but it has traditionally involved thieves stealing people’s mail or going through their trash.

Robbery via wireless remote access is something relatively new, Vilker said. He said he has seen it only twice in Rhode Island and declined to discuss the Portsmouth case or identify the other case.

In general in these types of cases, he said, cyber-thieves remotely install a “keylogging” program on a target computer.

The keylogging programs travel on e-mail attachments and can hide themselves on a computer system, becoming virtually undetectable. These “trojan” programs record each keystroke made by the unwitting target and transmit the data to thieves.

In Portsmouth, the police sifted through reports of identity theft until they discovered two or three victims who had used their cards at Custom House Coffee. Then they called in the FBI and the Secret Service.

Former Custom House Coffee owner Robert Mastin said there were security measures on the computer system, “but they weren’t enough for some very sophisticated hackers.”

The security breach has been “totally fixed,” said Mastin. “The chances of it happening again are less than zero.” The police concur with that assessment.

Thomas Powers, resident in charge of the Secret Service office in Providence, confirmed that his office provided forensic assistance in the Custom House Coffee case. But he declined to detail what he said is a continuing investigation.

Hebert said his detectives have received training in cyber crime-fighting to the extent that they know “what to look for.” Then they alert state and federal law-enforcement experts “who understand exactly how to track these people down,” Hebert said.

The FBI and a federally financed civilian partner, the National White Collar Crime Center, encourage anyone who has been victimized by cyber theft to both report to local police and to file a complaint on their jointly sponsored Web site, the Internet Crime Complaint Center, at www.ic3.gov.

“All that information helps investigators develop a pattern” that will help them better track criminal behavior, said Craig Butterworth, spokesman for the center.

In 2008, IC3 received a total of 275,284 complaints, a third more than in 2007, according to the FBI and the National White Collar Crime Center. Credit and debit card fraud accounted for 9 percent of the complaints. The most frequent type was nonpayment or non-delivery of goods, followed by Internet auction fraud.

In all, the complaints represented a dollar loss of $265 million, a $25-million increase from the previous year.

Butterworth said officials believe that only 15 to 20 percent of online fraud gets reported to the Web site.

To protect their customers, Internet service providers generally include virus detection and firewall protection with their broadband services to ward off hackers.

But there are still ways that Internet users can be vulnerable, said Mark Matteo of Cox Communications, who works as a liaison with law enforcement.

“When you download files, when you open e-mail, or when you use an unsecured wireless network,” you can give thieves access to your computer, Matteo said.

When Cox installs a wireless network connecting two or more home computers, it arranges to scramble the Internet transmission, Quinn said. But any time there is a power outage, or the network router in the home is reset, the homeowner may need to encrypt the network again. Manufacturers of routers provide directions on their Web sites.

gmacris@projo.com