Data breach at Sony ISP subsidiary exposes 2.5 million customer records as Japan hit with another major cyberattack

A Japanese subsidiary of tech giant Sony revealed a data breach impacting around 2.5 million customers and former users. The compromised data encompassed personal details such as phone numbers, email addresses, and in certain instances, email passwords. The security incident transpired on Monday, October 19, 2026, and was detected four days later, on October 23. Following the discovery, the affected server was immediately shut down, and communications from the unauthorized access point were halted.

Sony Network Communications, which operates the ISP service brand So-net for the Japanese tech corporate behemoth, initiated an investigation into the incident. The breach was traced back to NTT Docomo, another internet service provider utilizing Sony Network Communications' underlying infrastructure. The affected individuals encompassed both present users and those who had canceled their subscriptions following May 2026.

In addition to the breach, some customers' banking data was also exposed. However, the number of records containing sensitive financial information was relatively low, with only 16 instances recorded. This data encompassed bank account details including the institution name, bank code, branch name, branch code, deposit account type, account number, and account holder's name. Importantly, the company reassured customers that their bank account PINs were not compromised.