SHINDO3

Tokyo Metro

Tokyo Metro Co., Ltd.

Email addresses~59,000records

POSSIBLE LEAKUnauthorized access · Contained

Open in the live monitor ▶
Disclosed
Sep 27, 2026
Detected
Sep 20, 2026
Detection to disclosure
7 days
Leak
Leak possible
Type
Unauthorized access
Status
Contained
Security spend
Measures, no amount
Compensation
Not announced
Corporate number
4010501022810

What leaked

ContactEmail address

How many

  • Email addresses ~59,000 records

Who is affected

  • Metpo members (addresses with email delivery stopped)

Cause

Unauthorized access by a third party (apparently from overseas) to an email-delivery server. A malfunction occurred on 9/20 and the access was found during the investigation. Details of the cause under investigation

Timeline

  1. Malfunction occurred
  2. Detected
  3. First disclosure
  4. Company issued an update

Response

  • Notified individuals
  • Phishing warning

Countermeasures at the suspected point of compromise, email notices to affected people, warnings about spoofed emails

What you should do

  1. Don't open links in emails from this company. The apology email itself may be fake
  2. Check the company's notice to see if you're affected

Lessons for companies

  1. Report to the PPC: preliminary in 3–5 days, final in 30 (60 if malicious)
  2. Run red teaming and AI-assisted hardening, and publish how much you invest

Sources