Winny - Anonymity

Anonymity

At the time of the two users' arrests, the Kyoto Police claimed to have "analyzed Winny's anonymity features" to track the users down, but did not disclose the exact method used. It later turns out, as the details of the method used were disclosed at Kaneko's first day of trial, that this statement was not entirely accurate — It was areas where Winny did not provide anonymity that the Police used to track users down.

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.