May 24, 2023 Administrative Guidance to Nippon Telegraph and Telephone East Corporation and Nippon Telegraph and Telephone West Corporation on Appropriate Responses to Telecommunications Accidents

Today, the Ministry of Internal Affairs and Communications (MIC) issued a stern warning to Nippon Telegraph and Telephone East Corporation (hereafter referred to as “NTT East”), led by President SHIBUTANI Naoki, and Nippon Telegraph and Telephone West Corporation (hereafter referred to as “NTT West”), led by President MORIBAYASHI Masaaki, regarding the serious telecommunications accidents that occurred on April 3, 2023. MIC urged them to ensure that similar accidents do not recur. In addition, MIC instructed NTT East and NTT West in writing to effectively implement various measures to prevent recurrences.

1. Background

On April 3, 2023, the significant accidents led to the partial suspension of the FTTH services, Internet-related services, and voice transmission services for emergency calls (hereafter referred to as “Internet communications services, etc.”) provided by both NTT East and NTT West. On April 28, 2023, MIC received separate serious accident reports from both companies in compliance with Article 28 of the Telecommunications Business Act (Act No. 86 of 1984).
The accident caused, with respect to NTT East, the voice transmission services for emergency calls to be unavailable or difficult to use for one hour and 43 minutes (with affected users of up to 186,000 lines, and the total time of the accident affecting the Internet communication services was two hours and 58 minutes with affected users of up to 359,000 lines). With respect to NTT West, the voice transmission services for emergency calls to be unavailable or difficult to use for one hour and 39 minutes (with affected users of up to 47,000 lines, and the total time of the accident affecting the Internet communication services was one hour and 39 minutes with affected users of up to 87,000 lines). The social impact was extremely large because Internet communications and other services have become important infrastructures for people’s lives.
The occurrence of such a serious accident would be detrimental to the interests of users and have a serious impact on social and economic activities. In light of this, MIC issued a strict warning to prevent similar accidents and has provided written guidance to prevent recurrences.
*The published materials are in Japanese only.