Mitsubishi Heavy Admits 'Possibility' Cyber-Attackers Stole Sensitive Data

A month after Mitsubishi Heavy Industries said there was "no possibility" that data was stolen after cyber-attackers infected 83 servers, the company now reports it's "possible."

Mitsubishi Heavy Industries, Japan's largest defense contractor, said it is possible that attackers who had breached its networks and infected several machines with malware had also stolen some sensitive information.

While it fell short of an outright admission, the company's statement was a slight reversal from previous claims that no data had been compromised.

Some information on the company's products and technology had been moved from one server to another, and it is possible the data had been transferred out of the company, Mitsubishi Heavy Industries said in a statement on Oct. 25. The company acknowledged the theft a day after Japanese newspaper Asahi Shimbun cited unnamed sources who claimed information had been stolen during the attack.

Previously, a Mitsubishi Heavy Industries spokesperson had said that although the attackers had uncovered some data, such as the IP addresses assigned to the systems, there was "no possibility of any leakage of defense-related information at this point."

"The company investigated the incident further and recognized the possibility of some data leakage from the server in question," Mitsubishi Heavy Industries said in the latest statement, emphasizing that it hasn't found actual evidence yet.

Sources told Asahi Shimbun that "sensitive information concerning vital defense equipment, such as fighter jets, as well as nuclear power plant design and safety plans" had been stolen. Mitsubishi Heavy declined to confirm whether the "unintended" data transfer involved any defense or nuclear technologies.

Mitsubishi Heavy detected the network breach in August but did not disclose it publicly until September. About 80 computers in the company's Tokyo headquarters and production sites such as shipyards and manufacturing plants were infected with malware. An analysis of the infected systems revealed at least eight different Trojans had been used in the attack, and at least one of them had been a keylogger program.

Japan's Defence Ministry criticized the company for not immediately notifying the government of the breach. "It's up to the defense ministry to decide whether the information is important. That is not for Mitsubishi Heavy to decide. A report should have been made," a spokesman for the ministry told Reuters at the time.

The latest revelation comes on the heels of a new report of a cyber-attack on members of the Japanese Parliament, according to Asahi. Attackers targeted government computers and a server used by three members of the lower house and harvested passwords and usernames belonging to approximately 480 members and staff, according to the report. The stolen credentials had been sent to a server in China.

It is likely that malicious adversaries stealthily monitored sensitive email and documents without being detected for at least a month. It also appears that the initial compromise happened in July when one of the members opened an email with a malicious Trojan attached to the message.

There is still no real evidence linking the Parliament attack to the Chinese government just because the server was based in China, according to Graham Cluley, a senior technology consultant at Sophos. "That fact alone is not a convincing reason to blame China for the attack," Cluley wrote on the Naked Security blog, noting that the attacker could have been acting alone without government or military backing. Another likely scenario is that perpetrators could have easily compromised servers around the world and this just happened to be in China.

"It's just as possible that a hacker in, say, New Zealand placed his malware on a compromised Chinese server," Cluley said.

He expressed a similar concern for more "real" evidence last month when local Japanese media reported that Chinese script was found in one of the Trojans found on Mitsubishi Heavy systems.