A Keio ransomware attack has disrupted business systems at the Japanese railway and hotel group. The company disconnected its network after discovering the intrusion on September 26, while initial reports point to hospitality disruption rather than railway operations.
Hotel Services Face Possible Delays
Keio Plaza Hotel Tokyo warned customers that some services could experience delays following the incident.
Meanwhile, local media reported disruption to payment systems. The available information suggests that the attack affected Keio’s hospitality operations, with no reported disruption to train services.
However, the company has not yet established the full extent of the damage.
Keio’s businesses include a railway network spanning approximately 85 kilometres and 69 stations, alongside a hospitality portfolio of 25 hotels.
Company Disconnects Network to Limit Damage
The incident came to light after a system failure in the early hours of Saturday, September 26.
Keio subsequently confirmed that ransomware had affected its group servers. It then shut down network access to prevent further damage.
The company reported the incident to police and brought in external specialists. Together, they are investigating how the attackers entered the network and which systems they affected.
Additionally, investigators are checking whether the intruders accessed information belonging to customers or business partners.
The company has not confirmed any theft of that information. As of the September 28 report, no ransomware group had publicly claimed responsibility.
Tokyo Metro Reports Separate Email Exposure
Separately, Tokyo Metro disclosed unauthorized access to its own systems over the same weekend.
That incident exposed approximately 59,000 member email addresses. According to Tokyo Metro, the affected systems held only email addresses.
The operator says it has identified and closed the security weakness that enabled the intrusion.
Tokyo Metro runs nine subway lines across approximately 195 kilometres and 180 stations. It carries an average of around 7 million passengers each day.
No Confirmed Connection Between the Incidents
Although both companies operate Japanese railway services, the available information does not establish a link between the attacks.
The Keio ransomware attack involved malicious software and disruption to business systems. By contrast, Tokyo Metro described unauthorized access to a system containing member email addresses.
Investigators have not established whether the same attackers targeted both companies or whether the incidents formed part of a coordinated campaign.
For Keio, the investigation continues into the entry point, operational impact and possible exposure of customer or partner data.
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