Information on the communications networks of Japan's Self-Defense Forces may have been leaked since an NTT Communications Corp. server in the country was accessed without authorization in mid-December, sources close to the matter said Monday.
The leak could have occurred up to the point in May when the Japanese provider of technology solutions detected cyberattacks.
An internal probe by the affiliate of Nippon Telegraph and Telecom Corp., Japan's telecommunications giant, found indications that information stored on the server had been stolen by a third party, the sources said.
The revelation came after NTT Communications said in late May that information regarding 621 client companies and organizations may have been leaked due to unauthorized access to its servers, but it did not release any of the names citing the need to maintain confidentiality.
The domestic server contained information about communications devices at a Maritime Self-Defense Force facility in Yokosuka, south of Tokyo, as well as of communication lines in about 10 SDF locations, sources with knowledge of the situation said earlier.
The Defense Ministry is investigating the case with the company suspecting that the possible leak could affect the operations of the SDF communication system.
On Monday, the sources said the hacking followed a series of cyberattacks on its servers in other countries.
NTT Communications' ongoing probe has found that a server in Thailand was hacked via a server in Singapore in September 2019, according to the sources.
Three months later, a server in the United States was accessed without authorization via the Thai server, before the Japanese server was attacked, they said.
In response to a question from Kyodo News, an NTT Communications spokesperson admitted that the server in Singapore was used in the intrusion as it was about to be removed and its security had not been updated at the time.
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