The National Police Agency will offer cash rewards of up to ¥3 million for information helping to solve a recent rash of online threats sent from virus-infected computers.
An outline of the cases and explanations of the "iesys.exe" virus have been posted on the NPA's website along with a notification of the rewards.
Four innocent people were arrested between June and September in Tokyo, Osaka, Kanagawa and Mie prefectures after email threats were sent from their computers, which were controlled by an outside party using the virus.
Police have been analyzing websites and communications records of the Yokohama Municipal Government, a kindergarten and other places where threatening email messages were sent.
The NPA reward system until last week was limited to homicide, kidnapping and other life-threatening crimes. It now also covers intimidation and other cases posing a significant hindrance to public duties or business activities.