Cyber Threat Intelligence
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Ransomware Victim Healthcare

Nippon Medical School Musashi Kosugi Hospital

Ransomware attack by Netrunner · Disclosed April 3, 2026 · 🇯🇵 Japan

www.nms.ac.jp/kosugi-h

Date Disclosed
Apr 3, 2026
2026
Threat Group
Netrunner
6 total victims
Country
🇯🇵 Japan
Industry
Healthcare

ThreatAI Analysis

Compiled from this incident record and the threat intelligence profile for Netrunner. Figures and technique mappings are quoted from the source data, not inferred.

About the Netrunner group

NetRunner is a ransomware group active from at least 2025 targeting diverse sectors including healthcare, telecommunications, manufacturing, and agriculture across Japan, Italy, the US, and Jordan, notably demanding a $100M ransom from Nippon Medical School Musashi Kosugi Hospital. Netrunner has listed 6 victims since April 2026.

Incident Analysis

Nippon Medical School Musashi Kosugi Hospital was targeted by Netrunner ransomware, one of the most active ransomware groups in our database with 6 confirmed victims globally. The attack was disclosed on April 3, 2026, when Nippon Medical School Musashi Kosugi Hospital appeared on the group's dark web leak site.

Nippon Medical School Musashi Kosugi Hospital is based in Japan , operating in the Healthcare sector. Japan ranks #11 globally for ransomware attacks, with 266 victims in our database.

Sector context: Healthcare organisations are high-value ransomware targets because patient data is extremely sensitive, regulatory penalties for breaches are severe, and operational downtime can threaten patient safety — all factors that increase ransom payment pressure.

Netrunner typically employs a double extortion model: first exfiltrating sensitive data from the victim's systems, then deploying ransomware to encrypt files. Victims face two simultaneous threats — paying to restore access and paying to prevent publication of stolen data. The group's leak site publishes victim names and exfiltrated data as leverage.

Data source: This incident record is sourced from public ransomware group leak site disclosures aggregated via the ransomware.live API. Disclosure date reflects when the victim was published on the leak site, which may differ from the initial date of compromise. This platform does not publish or link to stolen data. Last data update: Sep 8, 2026 06:00 UTC.

Frequently Asked Questions

Was Nippon Medical School Musashi Kosugi Hospital attacked by ransomware?

Yes. Nippon Medical School Musashi Kosugi Hospital was listed as a victim of the Netrunner ransomware group on April 3, 2026. The organisation is based in Japan and operates in the Healthcare sector. The disclosure appeared on the group's dark web leak site.

Which ransomware group attacked Nippon Medical School Musashi Kosugi Hospital?

Nippon Medical School Musashi Kosugi Hospital was attacked by Netrunner ransomware. Netrunner is one of the most active ransomware groups, having claimed 6 victims globally. The group typically employs a double-extortion model: encrypting the victim's files and threatening to publish stolen data.

When did the Nippon Medical School Musashi Kosugi Hospital ransomware attack occur?

The ransomware attack on Nippon Medical School Musashi Kosugi Hospital was disclosed on April 3, 2026. This date reflects when the victim was published on the threat group's leak site, which may differ from the actual date of initial compromise.

What data was stolen in the Nippon Medical School Musashi Kosugi Hospital ransomware attack?

The specific data stolen from Nippon Medical School Musashi Kosugi Hospital has not been independently verified by this platform. Ransomware groups typically exfiltrate data before encrypting systems and use the threat of publication to pressure victims. As a Healthcare organisation, Nippon Medical School Musashi Kosugi Hospital likely held patient records, medical data, and personally identifiable information (PII).

How can organisations protect against Netrunner attacks?

To defend against Netrunner and similar threat actors, organisations should: maintain regular offline backups tested for restoration; implement network segmentation to limit lateral movement; deploy multi-factor authentication on all remote access; use endpoint detection and response (EDR) tools; conduct regular phishing and security awareness training; and monitor threat intelligence feeds for indicators of compromise (IOCs) associated with active groups.