Cybersecurity1 min read

Japan: Over 14 Million Login Credentials Leaked From Six ISPs in Major Breach

Japanese telecom KDDI disclosed a breach exposing 14 million ISP customer credentials.

Aditya Raj

July 2, 2026 · 1 min read

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Japan: Over 14 Million Login Credentials Leaked From Six ISPs in Major Breach

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KDDI disclosed a breach of 14 million ISP customer credentials, one of Japan's largest data breaches, prompting a government investigation.

Japanese telecommunications giant KDDI has disclosed a data breach that exposed over 14 million login credentials across six internet service providers. The breach is one of the largest in Japan's history and has prompted a government investigation.

Cybersecurity breach visualization — The KDDI breach compromised data from 14 million ISP customers

Warning

Affected users should immediately change passwords for all accounts, enable multi-factor authentication, and monitor financial statements for unauthorized activity.

The compromised data includes usernames, hashed passwords, email addresses, and in some cases, billing details. KDDI has stated that the breach originated from unauthorized access to a third-party system used for customer management. The Japanese Ministry of Internal Affairs and Communications has launched an investigation into KDDI's security practices and is considering new regulations for ISP data protection.

Cybersecurity experts note that the use of legacy systems may have contributed to the vulnerability. KDDI is offering free credit monitoring to affected customers.

Key Takeaways

1 14 million credentials leaked from six Japanese ISPs via KDDI
2 Breach includes usernames, hashed passwords, and billing details
3 Third-party system vulnerability was the entry point
4 Japanese government has launched an investigation

Frequently Asked Questions

How many credentials were leaked?

Over 14 million

Who was the affected company?

KDDI, a Japanese telecom giant

What data was compromised?

Usernames, hashed passwords, email addresses, billing details

SOURCES

Aditya Raj

Editor-in-Chief

Senior technology journalist covering AI, cybersecurity, and the future of computing. With over a decade of experience in tech journalism, Aditya brings deep industry insights and analysis to every story.