China reportedly had ‘deep, persistent access’ to Japanese networks for months

Late last year, Nikkei Asia reported that Japan was planning to add thousands of personnel to its military cyber defense unit. Now, we might know why. According to a report from The Washington Post, hackers in China had "deep, persistent access" to Japanese defense networks. When the National Security Agency is said to have first discovered the breach in late 2020, NSA Chief and Commander of US Cyber Command General Paul Nakasone flew to Japan with White House deputy national security advisor Matthew Pottinger to report the breach to officials.

Despite briefings that reached as high as Japan's prime minister, The Post reports that hacking from China remained an issue for several months, persisting through the end of the Trump administration and well into early 2021.

US Cyber Command initially offered Japan assistance in purging its systems of malware but were reportedly rebuffed because the country was not comfortable with another nation's military accessing their systems. Instead, Japan elected to use domestic commercial security firms to find vulnerabilities, relying on the US only for guidance on what those firms found. Japan would eventually adopt a more active national security strategy, which is said to include a new cyber command to monitor networks around the clock, and as many as 4,000 active cybersecurity personnel.