The software takes its name from WinMX, where the M and the X are raised one letter in the Latin alphabet, to N and Y. According to a 2006 report by the Recording Industry Association of Japan, upwards of three million people had tried Winny, and it has alternated with WinMX as the most popular file-sharing program in Japan.
Like Freenet, each client functions as a node. Initially, a search will return few results, but one can set up "clusters" based on certain keywords, and over time, your client will learn the best route to obtain the information sought.
The software was developed by Isamu Kaneko, who is a research assistant in graduate course of computer engineering at the University of Tokyo in Japan. He was also once a researcher at the Japan Atomic Energy Research Institute Kaneko originally anonymously announced his intent of developing the software on the Download Software board of the popular 2channel (2ch for short) Japanese bulletin board site. Since 2ch users often refer to anonymous users by their post numbers, Kaneko came to be known as "Mr. 47" ("47-Shi", or 47氏 in Japanese), or just "47".
On November 28, 2003, two Japanese users of Winny, Yoshihiro Inoue1, a 41 year-old self-employed businessman from Takasaki, Gunma Prefecture and an unemployed 19-year-old from Matsuyama, were arrested by the Kyoto Prefectural Police. They were accused of sharing copyrighted material via Winny and admitted to their crimes. Shortly following the two users' arrests, Kaneko also had his home searched and had the source code of Winny confiscated by the Kyoto Police.
On May 10, 2004, Kaneko was arrested for suspected conspiracy to commit copyright violation by the High-tech Crime Taskforce of the Kyoto Prefectural Police.
After Winny's development was stopped, Share was started by an anonymous Japanese engineer to pick up where Winny left off.
After failing to crack Winny's encrypted communications used in its file sharing feature, the Kyoto Police switched to a different method, namely tracking users via Winny's integrated forum feature. Unlike its file sharing feature, the forum feature of Winny provided anonymity for users who accessed message threads, but not for creators of threads. Users accessing threads were able to determine the IP address of the originator of the thread.
The Kyoto Police first looked for a thread where its originator was posting the file names of copyrighted material he was sharing, and recorded his IP address. They then configured their firewall to only allow connections to them from the thread owner's IP address. Finally, they confirmed that they could indeed download the copyrighted file from the user who stated (on his thread) that he was sharing it.
In one of the posts in 2ch Download Software board, "47" had pointed out that '... beta 8.1 [of Winny] has a security hole and is not anonymous. Don't exchange illegal files [with it].' . Critics claim that this is one evidence of Kaneko's malicious intent, as that "47" was advising users not to share copyrighted material on beta 8.1 because it was not anonymous and infringing users could be traced.
Others have said that Kaneko's action shouldn't constitute a crime, since he didn't infringe copyright himself, but that he just created software that could be used for that purpose. They also state that the claims of Kaneko's intent by his critics are unprovable (or outright false), as Kaneko's noted statements are too vague to be interpreted as having the intent claimed by critics. According to the Free Kaneko website, he warned users not to share illegal material using the software.
Some versions of Antinny work as follows:
Some people have uploaded their information unwittingly from their computers because of Antinny. That information includes governmental documents, information about customers, and people's private files. Once the information is uploaded, it is hard to delete.
Recently, highly publicised cases of sensitive file uploading have come to light in Japan's media. In particular, a military agency was forced to admit that classified information from the Maritime Self Defence Force was uploaded by a computer with Winny software installed on it.
Following this, ANA (All Nippon Airlines) were also the victims of an embarrassing data leak, with passwords for security-access areas in 29 airports across Japan being leaked over the program. This follows a similar incident with JAL Airlines on 17th December 2005, after a virus originating from Winny affected the computer of a co-pilot.
Arguably the biggest Winny-related leak however, is that of the Okayama Prefectural Police Force, whose computer leaked data on around 1,500 investigations. This information included sensitive data, such as the names of sex crime victims, and is the largest amount of information held by Japanese police to have ever leaked online.