Over the last several months, new cases of information disclosure have been reported by the media nearly every day in Japan. These incidents are often caused by variants of the W32.Antinny worm that targets the Winny P2P file-sharing network. Once W32.Antinny infects a computer, it captures a screen shot and searches for Microsoft Office documents, email folders, and photos on the compromised computer and uploads these files to the Winny P2P network. Then, not only the author of the worm but also any other Winny users can download that information.

Winny is a P2P program that has several interesting features, one of them being anonymity. Users can search and download files from the Winny network, but noone can know who has the file or where the file is from because Winny hides this information from users. Users can only access the filenames that are available for download from the network. Another interesting feature is the way in which newly downloaded files are shared....