Data leaks due to cyberattacks in Japan reached a five-year high by mid-October 2026, already surpassing previous full-year totals amid a surge in breaches at smaller businesses.
Cases Up to September 2026 Already Surpass the Previous Year
A survey by Tokyo-based market research firm MM Research Institute found that cyberattacks resulted in 454 information leaks in Japan between January and September 2026, up 49% from 304 cases in the same period last year. By October 13, the total had reached 485, surpassing the 432 recorded in all of 2025 to hit a five-year high.
By company size, 195 of the leaks between January and September 2026 hit firms with 300 or fewer employees, which is nearly double the figure from the previous year. Incidents at companies with 301 to 1,000 employees rose 25%, while those with 1,001 or more climbed 33%.
Categorized by initial point of entry, server encryption by ransomware was the leading threat for small and mid-sized firms (300 or fewer workers) at 45 cases. Account takeovers of employee email, social media, or workplace chat, along with system intrusions exploiting software vulnerabilities, were the next most common.
Of the incidents reported between January and September 2026, 164 cases (36% of the total) involved external parties, such as contractors or cloud service providers. This suggests an expanding pattern of cyberattacks targeting small and medium-sized companies integrated into the supply chains of larger corporations.
A breakdown by industry shows that between January and September 2026, cyberattacks targeting the information and communications sector jumped to 88, up roughly 2.7-fold over the same period of the previous year. Software and cloud providers, as well as media outlets such as publishers and broadcasters, were the target of numerous cases of unauthorized access to cloud services, development platforms, and business-chat accounts, leaking data belonging to client companies and readers. Manufacturing cases also rose 54%, from 52 to 80. The survey, noted that ransomware attacks and attacks on servers at overseas offices and group companies were particularly prevalent.
Incidents in the education and learning support sector increased roughly 1.9-fold over the previous year, from 24 to 45 cases. Universities and schools also experienced a notable number of phishing incidents and hijacked accounts involving faculty, staff, and students.
- Data on cyberattacks (Japanese) from MM Research Institute
(Translated from Japanese.)
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