Overview
Affected: mail services of STNet, KDDI Web Communications (CPI), JCOM, Chubu Telecommunications, NIFTY and BIGLOBE. The July 6 report (updated July 21) confirmed email addresses of 12,231,954 people leaked, including passwords of 7,616,173 (a subset). au-branded mail runs on separate systems and was unaffected. The Ministry of Internal Affairs and Communications ordered a report on June 24. Each ISP's impact is recorded separately and must not be summed.
Timeline
- Occurred
- Discovered
- Disclosed
Intrusion found; system patched.
Announced (up to 14.22M possibly affected).
Report filed; confirmed counts published.
Organization response
Per the notice, the organisation investigated and contained the incident, notified individuals and offered monitoring or protective resources.
What you can do
Be wary of emails, SMS or calls impersonating the organisation; do not open links or attachments or enter passwords or card details. Change reused passwords on other services.
Sources
- ISP事業者向けメールシステムに対する不正アクセスの発生についてKDDI株式会社 · 2026-11-09
- KDDI株式会社に対する報告徴収総務省 · 2026-11-09
- ISP事業者向けメールシステムに対する不正アクセスについてのお詫びとご報告KDDI株式会社 · 2026-11-09