Sony Network Communications has disclosed a major data breach affecting approximately 2.58 million member records associated with its So net internet service and plala S Course. The incident exposed personal information, while a separate set of 54,401 email accounts had their email addresses and passwords compromised.
The company disclosed the incident on October 27, 2026, confirming that an external party had gained unauthorized access to the So net member database. The investigation is ongoing, and the company has apologized to affected customers.
According to Sony Network Communications, the breach affected 2,141,986 So net member records and another 443,495 records associated with plala S Course, bringing the total to 2,585,481 records.
The affected So net records include 1,869,771 current members and 272,215 former members who cancelled their subscriptions in or after March 2026. The plala S Course figures include 422,365 current members and 21,130 former members who cancelled during the same period.
The exposed information includes names, telephone numbers, email addresses, user IDs, dates of birth, gender, and internet connection IDs. The company stated that passwords associated with these general membership records were not leaked.
However, the breach also affected several email services operated by So net, making the incident more serious than a straightforward exposure of customer contact information.
Sony Network Communications confirmed that email addresses and their associated passwords were leaked for 54,401 accounts across four email services.
The affected services include:
- Email Service (G): 24,655 accounts
- A Box: 17,672 accounts
- So net VAIO Mail: 7,005 accounts
- PostPet Mail Account Service: 5,069 accounts
The company reset the affected email passwords on October 27 and instructed users of these services to create new passwords through their So net account page.
This distinction is important. Although the company says the passwords associated with general So net and plala membership records were not leaked, passwords for the specific email services listed above were compromised.
The incident also exposed 16 sets of bank account information, including financial institution names, branch details, account numbers, and account holder names. The company stated that it does not hold bank account PINs. Additionally, information contained in seven password reset notices was exposed.
Sony Network Communications said that no credit card information was included in the leaked data.
According to the company's official disclosure, the unauthorized access occurred on October 19, 2026. The company confirmed the incident on October 23, shut down the affected server, and blocked communications from the source of the unauthorized access.
An investigation completed on October 24 confirmed the exposure of personal information and helped establish the number of affected records.
The company has reported the incident to Japan's Personal Information Protection Commission and is continuing to investigate the cause of the breach and its full scope. The exact method used to gain unauthorized access has not yet been disclosed.
Sony Network Communications also said that, as of October 27, it had not identified any secondary damage resulting from the incident. However, the company warned that exposed information could be used in fraudulent emails, text messages, or telephone calls.
Customers who use the affected So net email services should follow the company's instructions to reset their passwords through the official account page. They should also avoid reusing compromised passwords on other services and change any matching passwords elsewhere.
Customers should remain alert for suspicious messages or phone calls that use their names, email addresses, or other personal details to appear legitimate. The company advises users not to respond to suspicious communications, click links contained in unexpected messages, or open unfamiliar attachments.
So net has said it will contact affected customers individually and is reviewing its security measures and information management practices to help prevent a similar incident.
The breach adds to the risks associated with large customer databases containing personal information and account credentials. While the full cause and potential consequences remain under investigation, the exposure of more than 2.58 million records, alongside tens of thousands of email passwords, makes this a significant security incident for Sony Network Communications and its affected customers.
