International multimedia news agency Reuters (News - Alert) reports that hackers have breached computers of biggest Japanese defense contractor Mitsubishi (News - Alert) Heavy Industries Ltd. As per the report, the hackers targeted submarine, missile and nuclear power plant component factories during this attack. In a statement, Mitsubishi Heavy Industries said that some information could have been stolen in the first known cyber attack on Japan's defense industry, wrote Reuters.

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

He added, “We can't rule out small possibilities of further information leakage but so far crucial data about our products or technologies have been kept safe.” The company spokesman admitted that Mitsubishi first noticed the cyber attack on August 11.

According to Reuters, a Japanese defense white paper released last month urged vigilance against cyber attacks after a spate of high-profile online assaults this year, which include big U.S. defense contractors like Lockheed Martin (News - Alert).

Japan’s Yomiuri newspaper said about 80 virus-infected computers were found at the company's Tokyo headquarters as well as manufacturing and research and development sites, including Kobe Shipyard & Machinery Works, Nagasaki Shipyard & Machinery Works and Nagoya Guidance & Propulsion System Works, wrote Reuters.

Citing unnamed sources, the Yomiuri newspaper stated that Kobe Shipyard currently builds submarines and makes components to build nuclear power stations, while the Nagasaki Shipyard makes escort ships, Reuters wrote. The paper further revealed that the Nagoya plant makes guided missiles and rocket engines.

“At least eight different kinds of computer virus including Trojan horse, which steals key information from infected computer hardware, were found at Mitsubishi Heavy Industries’ main office or production sites,” according to the Yomiuri newspaper.

“It's probably just the first that hacking attacks in Japan have been detected. It's consistent with what we've seen already with big American defense companies,” Andrew Davies, a cyber-warfare analyst with the government backed defense think-tank, the Australian Strategic Policy Institute, told Reuters.