Winny — Isamu Kaneko's File-Sharing Software and a Seven-Year Trial

Winny is a Japanese file-sharing program written by Isamu Kaneko, then a research associate at the University of Tokyo. According to the facts found by Japan's Supreme Court, Kaneko began development on 1 April 2002 and on 6 May 2002 published the first trial version on a website he had set up. It used peer-to-peer technology, in which users' computers connect to one another without a central server, and it was designed to make it hard to tell who was sending what. Winny is known as software that came out of the anonymous bulletin board 2channel, where its developer was called "47-shi" (Mr 47).

Winny went on to sit at the centre of two social problems in Japan: the illegal sharing of films and games, and mass leaks of information caused by a virus. Kaneko was arrested in 2004, and after more than seven years in court his acquittal became final at the Supreme Court on 19 December 2011.

How it was developed

The Supreme Court found that the purpose of development was to test whether a new file-sharing program combining anonymity and efficiency could actually work. Besides its anonymity function, Winny had clustering, multiple downloading and automatic downloading for finding and transferring files efficiently. The decision described it as software that could exchange varied information efficiently while preserving the secrecy of communications, with applications in many fields, but which could also be used to infringe copyright.

When publishing it, Kaneko added a note to his website asking users not to exchange illegal files with the software.

Arrest and charges

In September 2003 two users put 25 games and two films online for anyone to download, using Winny2. They were arrested by Kyoto prefectural police in November 2003 and convicted.

On 10 May 2004 Kyoto police arrested Winny's developer, the University of Tokyo research associate, on suspicion of aiding and abetting copyright infringement. The police said they had applied the abetting charge on the basis of Winny's development intent as posted on 2channel and elsewhere. The question the case turned on was whether a developer could be punished because users had used the software illegally.

Three courts

The Kyoto District Court accepted that the technology itself was value-neutral, but found Kaneko guilty of abetting because he knew Winny was widely used to infringe copyright and published it accepting that.

The Osaka High Court acquitted him, holding that awareness of how software is used is not enough; for abetting, the software must be offered in a way that recommends illegal use as its main purpose.

The Supreme Court rejected that standard as a misreading of Article 62 of the Penal Code. At the same time, to avoid an excessive chilling effect on software development, it held that knowing software might in general be used by others to infringe is not enough. Abetting is made out only where it is highly probable that a not-exceptional share of those who obtain the software will use it to infringe, and the provider knows and accepts this.

The decision noted evidence suggesting about 40% of the files circulating on the Winny network were unlicensed copyrighted works. But because Kaneko had constantly warned users against illegal use, in the notice on his website and in posts to the development thread, it found he could not be said to have known and accepted that degree of probability, and upheld the acquittal.

One of the five justices, Takehiko Otani, dissented. Pointing to the same 40% figure among other evidence, he found a high probability of infringing use and would have held Kaneko guilty of abetting.

At a press conference the next day Kaneko issued a statement saying he had fought the case for the many engineers who had become hesitant to develop software because of it. The head of his defence team said the more than seven years since the 2004 arrest had been a very large loss not only for Kaneko but for Japan's software engineers.

Antinny and the leaks

Alongside the trial, Winny became known for something else: information leaks caused by Antinny, a virus that spread through Winny. Large amounts of personal and corporate information leaked, and it became a social problem.

On 15 March 2006 the Chief Cabinet Secretary, Shinzo Abe, made an unusual appeal at a press conference: the surest way to prevent leaks, he said, was not to use Winny on your PC, and he asked the public to follow that advice. The National Information Security Center (NISC) warned that files obtained through Winny were untrustworthy — no one could tell who made them, when or where — and that slipping Antinny into them was easy. Because most Antinny variants infected machines regardless of operating-system vulnerabilities, and many were not detected even by up-to-date antivirus software, NISC said a clean reinstall of the operating system was the only way to be sure a PC was not infected.

NISC added that viruses like Antinny could also spread through other file-sharing programs, email attachments and websites, and that it had singled out Winny because leaks through it were occurring so often.

Afterwards

Isamu Kaneko died of an acute myocardial infarction on 6 July 2013, a year and a half after his acquittal became final.

How far can a developer be held responsible when software is used illegally? INTERNET Watch describes the Winny case as the first in which a court ruled on that question. File sharing's place in the story of the web is on the internet and web timeline, and viruses and leaks on the cybersecurity timeline. For an email worm from the same era, see ILOVEYOU.