Hackers gained access to the computers of the biggest defense contractor in Japan, the manufacturer of Patriot Advanced Capability 3 missiles, targeting the submarine, missile and nuclear power plant component factories.

The Japanese company, Mitsubishi Heavy Industries Ltd, said that 45 servers and 38 PCs were infected with viruses at 10 facilities in Japan, including its submarine manufacturing plant in Kobe and a factory in central Japan that makes engine parts for missiles.

It is the country's biggest defense contractor with weapons including surface-to-air Patriot missiles and AIM-7 Sparrow air-to-air missiles. Mitsubishi Heavy has also been working closely with Boeing, making wings for its 787 Dreamliner jets.

The incident, which comes amid a heightened focus on cyber warfare refers to a politically motivated hacking to conduct sabotage and espionage. It is a form of information warfare sometimes seen as analogous to conventional warfare, although this analogy is controversial for both its accuracy and its political motivation. Only last week in a U.S. conference on cyber warfare, General Keith Alexander, the head of the U.S. Cyber Command, had stated that cyber attacks were escalating from large-scale theft and disruption of computer operations to more lethal attacks that destroy systems and physical equipment.

We've found out that some system information such as IP addresses have been leaked and that's creepy enough, said a Mitsubishi Heavy spokesman.

There were suggestions at the time that those attacks had originated in China as reported by Reuters.

At least eight different kinds of computer virus including Trojan horse, which steals key information from infected computer hardware, were found at Mitsubishi Heavy's main office or production sites, the Yomiuri newspaper reported.

The U.S has become extremely cautious about the cyber attacks and beginning September has pledged, along with Australia, to jointly thwart potential threats in cyberspace. “Cyber is the battlefield of the future,” Defense Secretary Leon Panetta had told reporters. “We are all going to have to work very hard not only to defend against cyber attacks but to be aggressive with regards to cyber attacks as well. The best way to accomplish that is not only on our own, but working with our partners.”

In addition to Australia, the U.S already has treaty ties with Japan, South Korea, the Philippines and Thailand. The White House, earlier this year, released its strategy for preventing and countering attacks on cyberspace, calling for responding to hostile acts in that domain “as we would to any other threat to our country.”