A Japanese man has admitted in court to writing a data-destroying Trojan horse. Twenty-four year-old Masato Nakatsuji, who was revealed to be the first ever virus writer to be arrested in Japan when he was apprehended in January, admitted in Kyoto District Court that he created a Trojan horse and used copyrighted animation footage to spread it via the net. Nakatsuji has admitted to having written the malware which displayed images of popular anime characters while wiping music and movie files from users' computers. The malicious code, believed to be the Pirlames Trojan, was spread via the controversial Winny file-sharing system in Japan last year.

Nakatsuji made the admission during the first day of the trial, where he answered charges of copyright infringement and defaming an acquaintance by embedding his photograph into the malicious code.

The court in Kyoto heard prosecutors describe how Nakatsuji is alleged to have created the Trojan horse, attached it to copyrighted animated pictures and planted links to it on Internet message forums. However, Nakatsuji's defense team has argued that the malware was not seriously malignant, and that justice would not be served by punishing the graduate student of Osaka Electro-Communication University for spreading the Trojan horse when there were no specific laws against it.

"Al Capone was charged with tax evasion rather than racketeering, and Masato Nakatsuji is being charged with copyright infringement rather than for creating his movie and music-munching malware," said Graham Cluley, senior technology consultant for Sophos. "If he is found guilty, the general public are unlikely to worry that it was his ill-advised choice of graphics which got him into legal trouble rather than virus-writing. However, a clear message needs to be sent to the computer underground that they will not be shown a blind eye if they spread malicious code and damage innocent people's computers and data." 

Isamu Kaneko, the author of the Winny file-sharing program, was fined by a Japanese court in December 2006 for assisting in copyright violation. The rights and wrongs of the case have been widely debated on the Internet.