Sincere Corporation Listed by thegentlemen Ransomware Group: Ransomware Claim — What’s Alleged & What To Do
Sincere Corporation has been listed by thegentlemen ransomware group, with internal files reported exfiltrated in an attack that came to light on January 20, 2026. An undisclosed number of people may have been affected; individuals are advised to check whether their information was involved and to monitor their accounts.
Inside the incident
The listing appeared on January 20, 2026. Public information states that internal files were exfiltrated during a ransomware attack against Sincere Corporation. No confirmed count of records, no timeline for the intrusion itself, and no description of the initial access method have been released. The group’s leak-site posting constitutes the sole public attribution at this stage.
Who is thegentlemen?
Thegentlemen is a ransomware operator that lists victim organisations on a dedicated leak site after claiming to have stolen data. Such groups commonly combine file encryption with the threat of publication to pressure targets. The present case rests on the group’s own claim of having placed Sincere Corporation on that site; independent confirmation of the data’s authenticity or volume has not been published.
Who is Sincere Corporation?
Sincere Corporation is a Japanese environmental services firm founded in 1969. It provides waste management, recycling, building maintenance and environmental consulting services across multiple prefectures, with major facilities in Shinagawa and Yokohama. Organisations of this type routinely process operational records, client contracts, regulatory submissions and employee information as part of nationwide service delivery.
What data was at risk
The only detail released is that internal files were taken. The precise categories of information contained in those files have not been disclosed. Companies in the environmental services sector typically maintain records that include customer agreements, compliance documentation, facility maintenance logs and personnel data, yet the exact contents of the exfiltrated material remain unconfirmed.
Why it matters
Exposure of internal operational files can reveal business relationships, regulatory compliance details and contact information that may be repurposed for targeted fraud or further attacks. For the organisation, the incident adds the costs of investigation, potential regulatory scrutiny and the need to restore systems while maintaining essential public services. Individuals named in the files face the standard downstream risks associated with any leakage of corporate records whose sensitivity is not yet fully mapped.
What to do if you're exposed
Anyone who has done business with or worked for Sincere Corporation should treat the situation as an unconfirmed but plausible exposure of internal records.
- Review recent account statements and credit reports for unusual activity.
- Enable multi-factor authentication on any services that hold personal or financial data.
- Consider a credit freeze if the files are later shown to contain identity-related information.
- Run a free exposure scan of your email address against known breach repositories to check for additional appearances.
AICompiled with AI assistance from public sources and published under our editorial standards.
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Publicly posted by thegentlemen — 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.