A computer virus that targets the popular file-sharing program Winny isn't the most destructive bug or even the most widespread. But it's the most talked about in Japan as it generates headline after headline, month after month.
The malware, called Antinny, finds random files on Winny users' PCs and makes them available on the file-sharing network. So far, the data leaked have been varied and plentiful: passwords for restricted areas at airports, police investigations, customer information, sales reports, staff lists.
The constantly updated virus seems to have spared no one — airlines, local police forces, mobile phone companies, the National Defense Agency. Even an antivirus software manufacturer has suffered.
"The virus has been quite effective in getting information off a user's computer and onto the Internet. The data is supposed to be secret, so people are quite sensitive about it," said Tsukuba University computer scientist Kazuhiko Kato.
Compared to attacks on Microsoft Corp.'s Windows software, the scope of the Antinny outbreak is narrow. But the Winny mess has caused an enormous brouhaha in Japan.
Antinny also may have the dubious distinction of being the first virus to exploit the nature of file-sharing itself — in Japan, if not in the world, said Mamoru Saito of Telecom Information Sharing and Analysis Center Japan. Other viruses and spyware are often found on such networks, though none appears to take advantage of the underlying technology to spread personal data.
And while Antinny's writers seem to be limiting themselves to Japanese file-sharing software for now, he said, the code theoretically could be modified to attack other file-sharing networks such as Gnutella and BitTorrent.
The outbreak has triggered a broad damage-control effort by government and businesses. They have banned Winny from in-house computers and fired employees who use it on them. They've also demanded that staff not take work home and delete Winny from any home PCs used for work.
"The most secure way to prevent the leakage of information is not to use Winny on your computer," Chief Cabinet Secretary Shinzo Abe, the government's top spokesman, told reporters.
But the outbreak shows little sign of abating.
"The problem has shown that many people just don't know how to use the Internet safely," said Takeshi Sato of the government's National Information Security Center.
File-sharing programs like Winny are used to find and get files — from music to video to documents — from the computers of other people also using the software. The PC owner typically has control over what is made available by limiting sharing to a specific folder.
The virus takes advantage of this culture to propagate itself by playing a "social" trick on users, said Telecom ISAC Japan's Saito.
When the virus is activated on a computer, it first chooses a new name for itself by taking the names of other files users are likely to be searching for — usually photos or music. The resulting new name becomes so long that, under normal Windows' settings, the three-letter file extension that indicates the type of file disappears from view, he said.
Careless users who download the file will see only the name and think it is something they wanted — say, a photo of a favorite movie star. They don't see that they are actually trying to open an application, not a picture.
When they do, the virus then looks on the computer for the Winny application, grabs random files off the hard drive and uses Winny to make those files — and itself — available for download on the network.
And so the cycle repeats.
Virus variations multiplying
New strains of Antinny appear all the time. Software maker Trend Micro listed 46 variations of the virus in its database as of mid-May. Trend itself lost sales data due to a Winny leak in 2005.
"Just keeping your antivirus software up to date isn't enough, because the updates can't keep up with all the new strains of the virus," the government's Sato said.
The government's concerns about Winny go beyond viruses. It's often used to share files — and that often means illegally exchanging copyrighted materials.
Winny was already on the government's radar screen in November 2004, when its creator — then an instructor at the prestigious University of Tokyo — was handed a three-year suspended sentence on charges of violating copyright laws.
But now it is confidential data rather than hit songs that have Winny back in the spotlight.
Japan Airlines, for example, discovered last December that an Antinny-infected computer owned by one of its co-pilots leaked passwords for restricted areas at 16 airports around Japan as well as Guam's international airport. The airline was forced to alert the airports to have passwords changed as a precaution.
In early March, Japan's National Defense Agency said it lost "confidential information" due to a Winny leak, again from an employee's home computer. While defense officials refused to say what data had been lost, a news report said it included reports on training exercises conducted in Okinawa with U.S. troops in 2005.
In the aftermath of the leaks, the agency ordered employees not to use Winny on any computers used for work. It also announced plans to purchase 56,000 computers so employees would no longer have to use their own equipment for work.
Schools, Internet providers and electric companies are among the others who can tell of similar losses. Making matters worse, reports began surfacing in May that the virus was now attacking another Japanese file-sharing application called Share (pronounced "shah-ray"), opening the door to yet more embarrassing leaks.
The excitement being generated is all the more remarkable when one considers the outbreak's scale.
Because Antinny needs Winny to spread, both the virus and the files it picks up are limited to a small section of Internet users — anywhere from 300,000 to 600,000 people, based on government and industry estimates.
Government statistics show Antinny was responsible for a minuscule fraction of the 24,155 virus outbreaks reported between November 2005 and April 2006.
"Reports of the leaks make for good drama," Tsukuba's Kato said. "Still, they show that people need to be careful if they connect their computers to the Internet."
The government and businesses are trying to help, with everything from educational pamphlets and Web sites to free software that can remove Antinny, Winny or both. But there are limits to what they can do.
"The industry is providing information about how to deal with the problem," said Telecom ISAC-Japan's Saito. "The question is whether or not the users do anything about it."