Kyushu Electric Reports Major Data Breach Affecting 10.9 Million Customers

Kyushu Electric Power Transmission and Distribution Co. announced on June 8, 2026, that a missing unencrypted SSD contained personal records of up to 10.9 million customers. The SSD was lost during a routine backup process on April 27, 2026, due to capacity issues, prompting the use of external storage. The drive was stored in a cabinet with biometric access controls, which was found unlocked on May 26, 2026. The missing data includes customer names, addresses, phone numbers, and electricity usage data, but no financial information. The company has filed a police report and is investigating potential unauthorized removal. As of now, there is no evidence of data leakage, but the incident is considered the largest data breach in Japanese history. The Japanese Ministry of Economy has mandated a report on the incident by July 8, 2026.

Key Points: • Kyushu Electric lost an unencrypted SSD with data of 10.9 million customers. • The incident is the largest data breach in Japanese history, surpassing previous breaches. • The company is investigating the loss and has filed a police report.