China breached Japan's classified defense networks, The Washington Post reports

A leading US newspaper says Chinese military hackers compromised Japan's classified defense networks three years ago.

The Washington Post on Monday revealed the alleged cybersecurity breach by the Chinese military, citing sources in both Japan and the United States.

The report says, "Cyberspies from the People's Liberation Army had wormed their way into Japan's most sensitive computer systems."

It also says, "The hackers had deep, persistent access and appeared to be after anything they could get their hands on -- plans, capabilities, assessments of military shortcomings."

Washington Post: China hacked Japan's sensitive defense networks, officials say

The US National Security Agency reportedly discovered the breach.

The White House deputy national security adviser and other senior US officials flew to Tokyo to brief Japan's defense minister. They described China's breach as "one of the most damaging hacks in that country's modern history."

Breaking news | In the fall of 2020, the National Security Agency made an alarming discovery: Chinese military hackers had compromised classified defense networks of the United States’ most important strategic ally in East Asia.https://t.co/VQYYwCZrBD

— The Washington Post (@washingtonpost) August 7, 2023

The administration of US President Joe Biden was informed in January 2021 that Chinese spies were still in Japan's defense networks and that Japan's measures were not sufficient.

In November that year, a senior White House official in charge of cybersecurity visited Japan and discussed with Japanese officials how to respond to the Chinese hackers.

The Washington Post quote US officials as saying, "Tokyo has taken steps to strengthen its networks. But they are still deemed not sufficiently secure from Beijing's prying eyes, which could impede greater intelligence sharing between the Pentagon and Japan's Defense Ministry."

Speaking to reporters on Tuesday, Japan's Defense Minister Hamada Yasukazu said that he would not elaborate on the matter as it concerns capabilities of the defense ministry and the Self-Defense Force.

Hamada said that he has not confirmed any leaks of classified information kept by the ministry.

He said that Japan has taken a range of effective measures, and the Self-Defense Force's activities to complete its missions have never been affected by a cyberattack.