Was Sincere Corporation hit by ransomware?

Sincere Corporation was listed by the thegentlemen ransomware operation (Japan), and stolen data was published on the group's leak site. Darkfield tracks this disclosure with the original leak post, screenshot and group context.

Who is the thegentlemen ransomware group?

thegentlemen is a ransomware operator tracked by Darkfield. See the full operator dossier for its known victims, sectors targeted, IOCs and leak-site infrastructure.

What data was leaked in the Sincere Corporation breach?

thegentlemen published data attributed to Sincere Corporation. Darkfield captured the leak post and a screenshot of the listing.

Ransomware victim disclosure

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SINCERE Corporation (株式会社シンシア)

listed as Sincere Corporation · Claimed by Thegentlemen · listed 5 months ago

Age

since listed · data leaked

Status timeline

ListedJan 21, 2026
Data leakeddate unknown

At a glance

Group: Thegentlemen
Status: Data leaked
Country: Japan
Listed on leak site: Jan 21, 2026

About the victim

AI dossier — public-source company profile

SINCERE Corporation (株式会社シンシア) is a Japanese environmental services company specializing in industrial waste processing (including incineration and resource recovery), ICT equipment recycling, building/facility maintenance, and related consulting. The company operates major processing facilities in Shinagawa and Yokohama, with approximately 27 regional centers spanning Tohoku to Kyushu. It handles sensitive waste streams including infectious medical waste and confidential document destruction for healthcare and corporate clients nationwide.

Industry: Industrial Waste Processing, Recycling & Facility Maintenance
Address: Shinagawa and Yokohama primary facilities, with regional centers across Japan (headquarters inferred: Tokyo/Shinagawa area, Japan)
Founded: 2007

Attack summary

Severity: high — Data is marked as published (exfiltrated and released), and the company handles sensitive data from medical institutions, confidential document destruction, and ICT device data erasure — suggesting significant regulated and sensitive business data is likely involved. The breadth of the company's national operations amplifies potential impact.

The ransomware group 'thegentlemen' claims an attack against SINCERE Corporation with a disclosed status of 'data_published', indicating data has been exfiltrated and published. The leak post content was not accessible (blocked by a bot-protection page), so specific details of what data was stolen or whether encryption occurred cannot be confirmed from the post itself.

high

Data the group says was taken

AI dossier — extracted from the leak post

Corporate business data
Client/customer records
Medical institution contract data (infectious waste clients)
Confidential document destruction records
Employee information
Operational/facility records

What the group claims

Sincerehq.com SINCERE Corporation is a Japanese environmental services company operating under the philosophy of "Symbiosis with Nature," offering "one-stop" solutions in waste management and building maintenance across four main segments: Resource Cycling, Recycling Business, Environmental Improvement and Building Maintenance, and Environmental Consulting. Established in 1969, the company contributes to Japan's circular economy with nationwide operations, including major facilities in Shinagawa and Yokohama.

The leak post

captured from the group's site

Gentlecloud Protection 🛡️ Gentlecloud Verifying your browser... Initializing security checks... I'm not a bot

Sources

Victim sitesincerehq.com
Leak posthttp://tezwsse5czllksjb7cwp65rvnk4oobmzti2znn42i43bjdfd2prqqkad.onion

Source

Indexed 5 months ago

This page surfaces a public ransomware disclosure indexed by Darkfield. Original posts come from the operator's own leak site; we cross-check against ransomware.live, RansomLook and RansomWatch where applicable. Share this URL freely.

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Disclosure context

About thegentlemen

thegentlemen is a ransomware group that emerged in September 2025, operating with apparent financial motivations based on their broad targeting of commercial sectors. The group has documented 267 victims across multiple countries, with primary focus on the United States, Thailand, France, Brazil, and India. Their targeting strategy demonstrates a preference for high-value sectors including manufacturing, technology, healthcare, and financial services organizations. Given the group's recent emergence and limited public documentation from established threat intelligence sources such as CISA, FBI, or major security research firms, specific details regarding their country of origin, operational structure, attack methodologies, encryption techniques, and whether they employ ransomware-as-a-service models remain unclear. The relatively high victim count of 267 in a short operational timeframe since September 2025 suggests either an aggressive campaign pace or potential inflation of victim numbers through affiliate operations, though without corroborating intelligence reports, the group's exact operational capabilities and notable campaigns cannot be definitively established. Current intelligence indicates the group remains active as of late 2025, though comprehensive threat profiling requires additional validated reporting from authoritative cybersecurity sources. The group has been linked to 483 public disclosures across our corpus. First observed on a leak site on September 9, 2025; most recent post June 11, 2026. The operation is currently active.

Also tracked as: the gentlemen.

Timeline of this disclosure

January 21, 2026Sincere Corporation listed by thegentlemenon the group's public leak site

Other recent disclosures by thegentlemen

thegentlemen has been linked to 483 public victims on Darkfield. A sample of the most recent:

See the full thegentlemen dossier →

Sector and geography

Geographically, Sincere Corporation is reported in Japan, a country with 108 ransomware disclosures in our corpus.

If your organisation is affected

A listing by thegentlemen means Sincere Corporation appeared on a ransomware extortion site and data attributed to it has been published. If this is your organisation, or a supplier you depend on, the priority is to confirm the intrusion and contain it before the window to act closes.

Engage your incident-response team and preserve forensic evidence before remediating — do not wipe affected systems first.
Force a password reset and revoke active sessions for exposed accounts; rotate any credentials, API keys or certificates that may have been in the stolen data.
Assess regulatory notification duties (GDPR, NIS2, sector regulators) — many carry a 72-hour reporting clock from awareness.
Monitor for the data appearing on thegentlemen's leak site and across paste and breach channels, and brief downstream partners who may be exposed through you.

How we know this. Darkfield monitors public ransomware leak sites continuously, archiving every new disclosure and the data later released against the victim. Each entry on this page is sourced from the operator's own publication and cross-checked against complementary OSINT feeds (RansomLook, ransomware.live, RansomWatch). We do not collect or host stolen data — only the metadata, timestamps and screenshots needed to make the public disclosure searchable and accountable. Records here are corrected when the original post is edited, retracted, or merged with another disclosure.