Hacking attacks against corporate computer systems in Japan, many powered by AI tools, are seeing an explosive rise, particularly from October on. Personal data on some 260 million individuals, cumulatively more than twice Japan’s population, have leaked in around half a year.

Anyone Could Be a Victim

Cyberattacks targeting businesses are on the rise, with 260 million personal information records leaked since April in Japan, according to data released by the Personal Information Protection Commission. The pace accelerated particularly in October, with 830 cases of unauthorized access reported in the first half of the month alone.

Unauthorized Data Access Incidents Reported (FY2026)

The Personal Information Protection Commission, an external organ of the Cabinet Office, requires companies to report personal information breaches within three to five days of discovering them. With data leaks from cyberattacks on the rise, the Commission has for the first time released preliminary statistics on data breach incidents, based on reports filed by companies.

From April 1 through October 16, the Commission received reports of 2,094 data breach incidents, far exceeding the 1,256 incidents reported during the entirety of fiscal 2025. Monthly figures stayed below 200 from April through June before climbing past that mark in July and rising further in the months that followed. Then, in October, a staggering 830 incidents were reported in just the first 16 days. Of these, 588 affected fewer than 100,000 people, 18 affected between 1 million and 10 million, and four affected more than 10 million.

Many of these data breaches are thought to be engineered with the help of artificial intelligence tools, which are proving to be highly effective at probing systems and detecting and exploiting their vulnerabilities. As many companies use not only in-house systems but also cloud services, a single cyberattack on a cloud provider can have a ripple effect where multiple companies are affected. These types of incidents are becoming increasingly common.

Data Sources

(Translated from Japanese.)