SHINDO4

Mitsubishi Paper Mills Limited

Personal data4,209people

POSSIBLE LEAKFull name / Email addressUnauthorized access · Closed (final report)

Open in the live monitor ▶
Disclosed
Dec 2, 2025
Detected
Aug 29, 2025
Detection to disclosure
95 days
Leak
Leak possible
Type
Unauthorized access
Status
Closed (final report)
Security spend
Not checked yet
Compensation
Not announced

What leaked

IdentityFull name
CredentialsLogin ID, Encrypted password
ContactEmail address
Employment & HRDepartment, Job title

How many

  • Employees and former employees (total) 4,209 people
  • Employees 2,422 people
  • Former employees 1,787 people

Who is affected

  • Employees
  • Former employees

Cause

Attackers entered via a remote access device and made multiple remote connections to the company's servers and PCs

Timeline

  1. Intrusion began
  2. Intrusion stopped
  3. Detected
  4. Security NEXT report date; first notice date not checked

Response

  • Blocked the entry point
  • Forensic investigation
  • Notified individuals

Disabled remote access and isolated affected systems, outside forensic investigation, notification of affected people

What you should do

  1. Change this password and every account that reused it now. Weak passwords crack even when hashed or encrypted. Switch to a passkey where offered
  2. Don't open links in emails from this company. The apology email itself may be fake
  3. Expect targeted phishing posing as HR or interview contacts
  4. Check the company's notice to see if you're affected

Lessons for companies

  1. Patch internet-facing servers, VPNs and admin panels first. Exploits follow disclosure within days
  2. Report to the PPC: preliminary in 3–5 days, final in 30 (60 if malicious)
  3. Run red teaming and AI-assisted hardening, and publish how much you invest

Sources