A Japanese man named Masato Nakatsuji has been arrested and accused of writing a computer virus that replaces all the files on a person's computer with home-made manga images of squid, octopuses and sea urchins.

It's believed that somewhere between 20,000 and 50,000 computers have been infected by the Ika-tako virus, which translates to "Squid-octopus". It spread through the Winny filesharing network, disguised as a music file, and once run the malware works through the files of the hard disk, replacing each with an image of a marine invertebrate.

It's not the first time that Nakatsuji has been arrested for virus creation. In 2008 he was convicted of violating copyright after coding malware that replaced data with an image from anime series Clannad. He told the police in this case that he didn't think he'd be arrested again because he'd created the squid and octopus images himself, avoiding a breach of copyright.


This time, however, the police arrested him on charges of "property destruction", arguing that since the virus makes it impossible to retrieve the original computer files, those files have been destroyed. It's the first time that Tokyo's police have arrested someone for property destruction in connection with malware.

The virus sends the files that it replaces with squid anime to a server that's believed to have been set up by Nakatsuji. Police found data for around 20,000 users on the server. Nakatsuji told police: "I wanted to see how much my computer programming skills had improved since the last time I was arrested."