The Yomiuri Shimbun

Police have arrested a man on suspicion of storing a computer virus on his personal computer without legitimate reasons, the Metropolitan Police Department announced Thursday.

The MPD arrested 38-year-old Yasuhiro Kawaguchi of Ogaki, Gifu Prefecture, at his home Sunday immediately after investigators confirmed he was storing the virus in question on his personal computer.

The revised Penal Code, which was enforced July 14, bans storage of a computer virus for the purpose of infecting other computers. Violators can be sentenced to a maximum of two years in prison or fined up to 300,000 yen.

The virus found on Kawaguchi's computer works by repeatedly copying vast amounts of graphic elements and files on a computer, causing it to freeze or malfunction, according to the MPD.

The MPD suspects about 2,000 users of file-sharing software have been infected with the virus.

According to the MPD, it was the first case in the country after the revised Penal Code, which also prohibits the creation and distribution of viruses, was put into force this month.

Kawaguchi uploaded a file containing the virus, which was titled to suggest child pornography, to the Internet via the file-sharing software Share. People who downloaded the file and opened it on their computers, or activated a DVD onto which the file was saved, would cause their computers to be infected, according to the MPD.

Kawaguchi, unemployed, admitted storing the virus and told the MPD that he did it to punish people who use file-sharing software, according to the MPD.

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Police able to act quickly

The charge of storing a computer virus without a legitimate reason has been applied for the first time, on the basis of the revised Penal Code, thanks to a cyber-patrol investigation by the MPD.

The investigation found that a file containing the virus had been distributed on the Internet via a file-sharing software called Share.

As MPD investigators searched Kawaguchi's home, the virus was found stored on his personal computer. He was caught immediately and arrested.

"Thanks to the revised Penal Code, we were able to take quick action, preventing the virus from causing more harm" said a senior MPD official.

Before the revision of the law, there was no law that enabled police to directly keep surveillance on virus creators, leaving police to catch virus creators using various laws and ordinances, including the Copyright Law, or by applying charges of property destruction.

On Wednesday, the Tokyo District Court sentenced a man to two years and six months in prison without suspension on charges of property destruction for creating a computer virus that replaced files on infected computers, destroying the original files.

The latest virus would not damage data on infected computers, but would cause a glitch in their operation.

"It might have been difficult to apply the charge of property destruction in this case," the senior MPD official said.

"In the past, we came up with different strategies using various laws and regulations," said another senior MPD official. "With many new types of viruses constantly appearing on the Internet, we were unable to keep up. Now, the revised Penal Code will become a powerful weapon."

Kawaguchi told police that he started creating viruses in about 2007, and police believe he created the latest virus. However, police plan to build a case against him on the charge of storing the virus, rather than creating it, as it was created before the revised law took effect.