Data Breach Exposes Millions of Email Logins at Japanese ISPs

Recently, KDDI Corporation, a prominent Japanese telecommunications operator, revealed a significant data breach that compromised the email systems of five other internet service providers (ISPs) in Japan. The breach, discovered on June 17, was promptly addressed by KDDI, who took immediate action to block the attackers and strengthen their defenses.

An investigation into the breach determined that the hackers exploited a vulnerability in a third-party software utilized by KDDI Corporation.

KDDI Corporation has cautioned that despite implementing technical defensive measures, there is a possibility that unauthorized third parties may have accessed customers’ email addresses and passwords.

Scope of the Breach

As one of Japan’s largest ISPs with a substantial workforce and revenue, KDDI Corporation’s breach also impacted five other ISP operators and their email services, including STNet, Inc., JCOM Co., Ltd., Chubu Telecommunications C., Inc., NIFTY Corporation, and BIGLOBE Inc.

While the exact number of affected accounts is still being investigated, KDDI estimates that up to 14.2 million customer accounts may have been exposed, including current and former customers as well as inactive accounts.

Although some passwords were stored in hashed or encrypted form, providing a level of security, KDDI did not disclose the encryption methods used or the percentage of accounts with plaintext passwords.

KDDI has informed the relevant authorities and is collaborating with the affected ISPs to enhance security measures. Customers are advised to reset their email passwords and enable two-factor authentication for added protection.

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