IDC Frontier (Tokyo), a SoftBank subsidiary that provides cloud services, announced on October 14 that an investigation conducted with outside security specialists has concluded that no customer data was leaked externally in the ransomware attack that occurred on October 7. The company said no traces were found indicating that information on the affected servers had been queried or exfiltrated by outside parties.
In the early hours of October 7, the company’s enterprise cloud service systems were subjected to unauthorized third-party access, causing a large-scale outage. The attack, carried out using ransomware — a type of computer virus that demands ransom payments — affected 495 businesses and municipal governments. As of October 8, the company had indicated that restoring some of the stored customer data would be difficult.
In its October 14 announcement, the company said that a detailed review of the attacker’s entry path and operation history found no evidence that data had been taken outside. No unauthorized use of information has been confirmed to date, and the company expressed its view that there is no risk of secondary damage. Affected customers are being notified individually, starting October 14, that no data leak occurred.
Meanwhile, the outlook for restoration remains uncertain. The company declined to answer questions regarding details of the attack, including the entry path, stating that a full investigation may still take time.
194 Customers Can Restore Data from Backups
The announcement also revealed new information regarding the possibility of data restoration. Of the 495 affected businesses and municipal governments, 194 customers were confirmed to have been using the backup function, making their data retrievable.
Previously, the company had indicated that retrieving or restoring data for affected customers would be difficult. However, as the investigation progressed, it was discovered that some data could be restored from backups. While the company maintains that restoring the stored data itself remains difficult, for the 194 customers — roughly 40% of those affected — this represents a significant step toward business continuity.
ItemDetailsAffected businesses and municipal governments495Customers confirmed restorable from backups194Date of outageEarly hours of October 7, 2026Attack typeRansomware
Note: Based on IDC Frontier’s announcement as of October 14.
Prolonged Cloud Outage Casts Shadow over Business Operations
IDC Frontier provides cloud infrastructure to numerous businesses and municipal governments across Japan, and the outage has had widespread impact on customer operational systems. The fact that no restoration timeline has been established even one week after the incident represents a major business continuity risk for customers with high dependence on the service.
The announcement that no data was leaked offers some reassurance to customers. However, with the timing of system restoration still unclear, affected businesses and municipal governments continue to face pressure to secure alternative solutions and review their operational processes.
A large-scale outage of domestic cloud infrastructure caused by a ransomware attack is exceptional in scale even by recent standards, once again highlighting the risks of corporate dependence on external cloud services. For the SoftBank Group as a whole, the subsidiary’s incident response and customer compensation will be key areas of focus going forward.
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