INSPECTING ARCHIVED INTELLIGENCE (OUTDATED VERSION).

Nikkei Experiences Data Breach Affecting Over 1.8 Million Records

| 2026-10-20 18:00 HIGH LOW DATA BREACH
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Executive Summary
AI-generated
A data breach at Japanese media company Nikkei Inc. affected over 1.8 million records, with hackers using stolen credentials to access a cloud service for system development on October 7. The attackers accessed the cloud service without authorization and leaked approximately 1.83 million items of personal information as of October 16. Of these, about 150,000 items contained one or more of name, email address, postal address, phone number, or date of birth, with around 120,000 including an email address. The breach did not compromise financial information and Nikkei has since blocked the stolen credentials. The company reported the breach to Japan's Personal Information Protection Commission on October 11 and is still investigating the scope of the security breach.
Technical Mitigations AI-generated
• Block the use of stolen login details, such as those used by Nikkei in this incident. • Regularly review and update cloud service access controls to prevent similar unauthorized access. • Use multi-factor authentication (MFA) for all users accessing system development services.
Intelligence Metadata
Actors / Malware / CVEs / Campaigns
Target & Sectors
JP
mediamedia
Incident Timeline
‎May 2022
Threat actors compromised a Slack account, leading to the data breach of Nikkei.
target_region Japan
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
tactic Data Breach
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
tactic Ransomware
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
organisation Slack
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
‎November 2025
Threat actors compromised a Slack account, leading to a data breach at Nikkei that affected over 1.8 million records.
target_region Japan
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
tactic Data Breach
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
tactic Ransomware
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
organisation Slack
In May 2022, the Japanese media giant Nikkei disclosed a ransomware attack, while in November 2025, it disclosed a data breach stemming from the compromise of a Slack account.
organisation SecurityAffairs
Follow me on Twitter:  @securityaffairs  and  Facebook  and  Mastodon Pierluigi Paganini ( SecurityAffairs  – hacking,  Nikkei )
‎October 7
Threat actors used previously stolen login details to gain access to a cloud service on October 7.
‎October 11
Threat actors exploited vulnerabilities to breach Nikkei's systems, resulting in the exposure of over 1.8 million records.
target_region Japan
The company reported the breach to Japan’s Personal Information Protection Commission on October 11.
‎October 16
Threat actors accessed a cloud service used by Nikkei Inc. without authorization, resulting in the leakage of approximately 1.83 million items of personal information.
tactic Data Breach
“A cloud service used by Nikkei Inc. for system development was accessed without authorization, and as of October 16, approximately 1.83 million items of personal information had been leaked.” reads the data breach notice published by the company.
organisation Nikkei Inc.
“A cloud service used by Nikkei Inc. for system development was accessed without authorization, and as of October 16, approximately 1.83 million items of personal information had been leaked.” reads the data breach notice published by the company.
general_metric 1.83 items
“A cloud service used by Nikkei Inc. for system development was accessed without authorization, and as of October 16, approximately 1.83 million items of personal information had been leaked.” reads the data breach notice published by the company.
‎2026/10/20
Hackers used stolen credentials to access a cloud service for system development, affecting over 1.8 million records at Nikkei.
data_breach 1.8 records
Japanese media company Nikkei has disclosed a data breach affecting more than 1.8 million records.
Nikkei data breach affected over 1.8 million records.
Nikkei data breach affected over 1.8 million records Nikkei disclosed a data breach affecting over 1.8 million records after hackers used stolen credentials to access a cloud service for system development.
organisation the Financial Times
The company, known for its financial news publications, including The Nikkei and the Financial Times, said attackers accessed a cloud service used for system development.
Tactical Metrics
Metrics
data_breach
1,800,000
Records
Nikkei data breach affected over 1.8 million records.
Nikkei data breach affected over 1.8 million records Nikkei disclosed a data breach affecting over 1.8 million records after hackers used stolen credentials to access a cloud service for system development.
Japanese media company Nikkei has disclosed a data breach affecting more than 1.8 million records.
Intelligence Sources
Security Affairs 2026-10-20