YOKOSUKA GAKUIN Listed by rhysida Ransomware Group: Ransomware Claim — What’s Alleged & What To Do
YOKOSUKA GAKUIN was listed by the rhysida ransomware group on December 15, 2025, after internal files were exfiltrated in an attack whose occurrence date has not been established. Individuals connected to the organisation should verify whether their information was exposed and take any recommended protective steps.
Breaking down the breach
The only confirmed detail is the December 15, 2025 listing by rhysida. No information has been released on the date of the intrusion, the method of initial access, the volume of data involved, or whether any data was subsequently published. The scale of exposure, including the number of people affected, is stated as unknown.
The group behind it: rhysida
Rhysida is a ransomware operator that has conducted multiple campaigns since at least 2023. The group typically gains access through phishing or compromised remote-access services, deploys encryption, and lists victims on a leak site to pressure payment. Its listings constitute claims by the group; independent confirmation of data theft or publication is required in each case.
YOKOSUKA GAKUIN and its sector
YOKOSUKA GAKUIN operates in the education sector. Institutions of this type maintain records related to students, staff, and institutional operations. A ransomware incident at such an organization can affect continuity of services and the confidentiality of records that are not normally public.
The information in question
The listing refers to internal files exfiltrated in a ransomware attack. No further breakdown of file categories or data fields has been provided. The precise contents therefore remain unconfirmed.
The real-world impact
Where internal files contain personal information, affected individuals may face risks of identity misuse or targeted fraud. For the organization, the incident may involve operational disruption and costs associated with investigation and recovery. The absence of disclosed details limits assessment of the scope of these risks.
What to do if you're exposed
Individuals connected to the organization should treat any notification from YOKOSUKA GAKUIN as the authoritative source of guidance. In the meantime, basic precautions include reviewing account statements for unusual activity and using unique passwords with multi-factor authentication.
- Change passwords for any accounts linked to the organization and enable multi-factor authentication where available.
- Monitor financial and government-service accounts for signs of unauthorized access.
- Run a free exposure scan of your email address against known breach data to check for prior appearances.
AICompiled with AI assistance from public sources and published under our editorial standards.
How this breach connects
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Publicly posted by rhysida — unverified claim, pending independent verification
Breach listings — particularly those originating from ransomware or leak sites — are third-party claims that may be unverified, incomplete, or inaccurate. A listing does not by itself confirm that a breach occurred or that any specific data was exposed. Severity is an automated assessment, not a definitive rating. Verification status is shown where available.
Attributions to threat groups and methods reflect public reporting and, in some cases, unverified claims made by the groups themselves; they may be incomplete or later revised. Recent Breaches and GalaxyWarden are independent and are not affiliated with, and do not endorse, any company or group named on this page. This information is aggregated from public sources for awareness only and is not legal, security, or investment advice.