Japanese telecommunications operator NTT DOCOMO has confirmed that unauthorized access to its servers resulted in the exposure of customer information, with up to approximately 300,000 records potentially affected.
The breach involved DOCOMO’s Online Shop and My docomo services. The company identified unauthorized external access on November 4, 2026, and confirmed the leakage in an update published on November 5.
Information exposed includes customers’ names, residential addresses, dates of birth, mobile telephone numbers and contact telephone numbers. DOCOMO has not yet published a complete list of the affected information, saying its investigation into the scope and number of exposed records is continuing.
Following the discovery, DOCOMO began emergency maintenance at approximately 1:05 a.m. on November 5, suspending various procedures through the two affected services. The company initially reported suspected unauthorized access to its servers in a notice published at 9:00 a.m. A subsequent update at 6:30 p.m. confirmed that customer information had leaked before the maintenance began.
The emergency maintenance remained in effect at the time of the second announcement. DOCOMO reported that it had blocked access and had not identified any additional information leakage since the maintenance started. It did not provide a restoration date for the affected services.
The company has not disclosed how the attackers gained access to its servers. The cause, intrusion route and precise scope of the exposure remain under investigation. It has also not established whether other information, including account credentials or payment details, was affected.
DOCOMO warned that the exposed information could be used to impersonate the company or people associated with it through fraudulent emails, SMS messages and telephone calls. Customers were advised not to open suspicious attachments, visit links in unexpected messages or provide personal information, passwords or credit card details in response to such communications.
Customers seeking assistance can contact DOCOMO’s information center through 151 from a DOCOMO mobile telephone or 0120-800-000 from other telephones. The telephone support service operates daily from 9:00 a.m. to 8:00 p.m.
The company said it would notify affected customers once it establishes the details of the exposed information.
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