What happened. NTT Docomo, Japan's largest mobile carrier, confirmed that external unauthorized access to My docomo and the Docomo Online Shop on Nov 4 led to a customer-data leak. Its Nov 6 third notice (as of 6:00 p.m. JST) puts the affected count at up to about 300,000 records. At a Nov 6 press briefing covered by ITmedia, Docomo put the line-based maximum at 294,839 (including canceled lines), of which 204,157 were individual contracts. Services were stopped from about 1:05 a.m. JST on Nov 5 and remain offline; restore timing is Undisclosed.
What was exposed. For all affected customers, Docomo lists names, dates of birth and age, addresses, contact phones and emails, identity-document numbers, mobile numbers and contract dates, plus plan, option and discount details. For some customers it also lists agent contact details, employer or corporate names and addresses, bank name/branch/account number/account holder, and childcare-program data. Company briefings say credit card numbers were not compromised. The intrusion path is still under investigation; Docomo describes the cause as external unauthorized access that searched linked systems mechanically after a mass-access alert around 10:30 a.m. JST on Nov 4.
Why this matters to an enterprise. Docomo is a household-name telco with corporate as well as consumer lines, and the haul includes identity-document numbers plus, for some accounts, bank details — exactly the fields used in follow-on phishing and account takeover. If you buy Docomo corporate SIMs or rely on My docomo for fleet changes, treat the outage as a forced change-control freeze, warn employees about Docomo-branded SMS and calls, and rotate any shared admin credentials used against Docomo portals.