Customers on NTT Docomo’s 5G standalone service faced disruptions to calls, data and texts across Japan, and the carrier said Thursday morning that investigators had not identified the cause.
Docomo said the outage began at 9:18 p.m. ET Wednesday, Nov. 4 (02:18 UTC Nov. 5). The company said other 5G and 4G users, mobile virtual network operators using its network, and emergency calls were not affected.
At 8 a.m. ET Thursday, Nov. 5 (13:00 UTC), Docomo said the disruption was continuing. It reported no signs of unauthorized access or a cyberattack around the network outage, whose cause remained under investigation.
In a separate notice, Docomo said it halted procedures on its online shop and My docomo at 11:05 a.m. ET Wednesday, Nov. 4 (16:05 UTC) after detecting outside access. An update at 4:30 a.m. ET Thursday, Nov. 5 (09:30 UTC) confirmed that customer information had leaked. The number of affected records remains under investigation, with up to about 300,000 cases potentially involved.
The exposed information may include names, addresses, dates of birth, mobile phone numbers and contact phone numbers. The notices did not say whether the leak and network disruption were connected.
Docomo had not set a restoration time for its online services. The company said it was investigating the intrusion’s cause, entry route and scope, and advised customers to watch for suspicious emails, texts or calls that might use the leaked information.
