Playing video games online, you're likely to run into cheaters. Aimbot, wallhacks, NoClip, they can render a server unplayable. However, they're little more than a pain in the ass, and penalties for getting caught can be pretty severe, including having accounts that cost a lot of money banned from using certain games. In Japan, they'll just arrest you.
Kotaku reports that the police pressed charges against three gamers for using cheats in a first-person shooter called Sudden Attack. Using these cheats violates the game's terms of service, something that has been unsuccessfully prosecuted in America in the past. It's a little unclear to me from the reporting on the story precisely what these gamers are being charged with. It's also unclear how the police came to press charges, but I would guess that Nexon, the makers of Sudden Attack fed the cops info about these gamers and asked them to prosecute. It'll be interesting to see if this prosecution is successful, and if it becomes a model for other countries.