Investigating

Nikkei: staff Microsoft 365 compromise may have leaked recipient data and sent about 9,000 malicious emails

Possible data leak: Staff Microsoft 365 accounts were compromised; about 9,000 spoofed emails were sent. Recipient emails/names and some message content appear leaked. Malicious mails on Sep 30, 2026; passwords reset; no further logins seen. Counts under review. Disclosed Oct 4.

Last updated: 2026-11-09

Overview

Counts under review → blank.

Timeline

  1. Occurred
  2. Discovered
  3. Disclosed

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

  1. サイバー攻撃による情報漏洩、不審メールの送信について株式会社日本経済新聞社 · 2026-11-09

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