Lanmark Group Listed by sinobi Ransomware Group: Ransomware Claim — What’s Alleged & What To Do
Lanmark Group was listed by the sinobi ransomware group on December 16, 2025, after internal files were exfiltrated in a ransomware attack. The number of individuals affected is not yet known; anyone connected to Lanmark Group should review their accounts and monitor for unusual activity.
Inside the incident
The only confirmed information is the date the listing appeared and the general description of the data as internal files. No timeline for the intrusion, method of access, or confirmation of encryption has been disclosed. The scale of the operation, including whether data was removed in addition to any encryption, is not specified in available reports.
Inside sinobi
Sinobi is a ransomware group that follows the common pattern of claiming data theft and listing victim organizations on a leak site. These groups typically use the listings to pressure targets into paying a ransom by threatening public release of the material. The listing of Lanmark Group constitutes the group’s claim; independent verification of the data’s presence or authenticity has not been reported.
About Lanmark Group
Lanmark Group, Inc. is a general contracting firm founded in 2005 and based in Brooklyn, New York. It handles complex construction projects for public and private sector clients, including multi-million-dollar work for state and municipal agencies. Organizations of this type routinely maintain records related to project bids, contracts, subcontractor information, safety documentation, and communications with government clients.
What was likely exposed
The listing refers to internal files exfiltrated in a ransomware attack. The precise categories of data within those files have not been disclosed. Construction and contracting firms commonly store project plans, financial records, employee and vendor details, and regulatory correspondence, but it is not confirmed whether any of these specific types were taken in this case.
Why it matters
Exposure of internal files from a contractor working with public agencies can affect ongoing projects, competitive information, and relationships with clients. For individuals whose data appears in such records, the main concerns are potential misuse of contact details or identification documents. The organization faces operational disruption and the need to review its security controls and incident response processes.
If your data was in this claimed breach
Monitor accounts associated with the organization for unusual activity and consider placing fraud alerts with credit bureaus if personal identifiers may have been involved. Review any communications from Lanmark Group for official guidance. Readers can run a free exposure scan of their email address against known breach data to check for prior appearances in public listings.
AICompiled with AI assistance from public sources and published under our editorial standards.
How this breach connects
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Publicly posted by sinobi — 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.