Japan’s top weapons manufacturer has been hit by a cyber attack. Officials at Mitsubishi Heavy Industries (MHI) said that its computer systems were hacked last month, and that attackers attempted to obtain data on the companies submarines, missiles and nuclear power plants. Forty-five of MHI’s servers are confirmed to be infected with a computer virus. Japan’s defence ministry is demanding MHI conduct a full investigation into the matter. It is believed that the cyber attackers used the so-called “spear phishing” technique, where hackers send emails that trick people into visiting websites and entering their login information. Neither MHI nor the Japanese government has given any indication of who might be responsible for the attack. One Japanese newspaper, however, has reported that Chinese language script was detected in the attack. China, for its part, vehemently denied any involvement. MHI has said it is conducting an investigation alongside Tokyo police, and will publish its findings by the end of September.