A third party gained unauthorized access to an external email delivery service used by the operator of Osaka Prefecture's online administrative system, and users' email addresses may have leaked, the prefecture announced on the afternoon of November 4.
Whether any addresses actually leaked, and how many, is still under investigation. Some functions, including user registration, are unavailable, and there is no estimate for when they will be restored.
Governor Hirofumi Yoshimura told a regular press conference at the prefectural government office the same afternoon that residents should not open files attached to suspicious email. "I would ask you not to open files in suspicious emails that arrive in your own inbox," he said.
The prefecture received a report from the system operator on November 2. User registration, changes to email addresses and password resets are currently impossible, while other functions remain available.
Yoshimura said the unauthorized access hit Arara, the company that handles email delivery. He said the only information that may have leaked is email addresses, and that names, addresses and credit card details are not believed to be included.
He warned that messages asking for card numbers or personal information may be fraudulent. "There are a very large number of information leak cases of various kinds," he said. "First of all, please do not open suspicious emails or files that arrive in your own inbox."
Yoshimura also urged residents not to register important details such as credit card information, and to never open files attached to suspicious email.