Was Tentac hit by ransomware?

Tentac 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 Tentac breach?

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

Ransomware victim disclosure

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TENTAC Co., Ltd

listed as Tentac · Claimed by Thegentlemen · listed 20 hours ago

Today

Age

since listed · data leaked

Status timeline

ListedSep 15, 2026
Data leakeddate unknown

At a glance

Group: Thegentlemen
Status: Data leaked
Country: Japan
Sector: Technology
Listed on leak site: Sep 15, 2026

About the victim

AI dossier — public-source company profile

TENTAC Co., Ltd is a Japanese manufacturer of robotic tool changers and automatic docking systems that enable industrial robots to swap end-of-arm tools mid-production. Founded in 1968 as a Kobe Steel division and spun off as independent in 1985, the company holds an estimated 80% global market share in robot docking systems and supplies major integrators including Fanuc, Kawasaki, Yaskawa, ABB, and KUKA. The company also produces inertial gyro sensors for marine and construction applications.

Industry: Industrial Robotics & Automation Equipment
Address: Kobe, Japan
Employees: 35–40
Founded: 1968

Attack summary

Severity: low — The leak post is a listing/announcement with no proof files, no data inventory disclosed, and no explicit statement of what was compromised or how. No operational impact is claimed.

thegentlemen claims to have conducted an attack on TENTAC Co., Ltd. The leak post does not specify whether data was encrypted, exfiltrated, or both, nor does it detail what data is claimed to be at stake.

low

What the group claims

tentac.co.jp zoominfo.com/c/tentac-co-ltd/458253608 TENTAC Co., Ltd world's leading maker of robotic tool changers — automatic docking systems that let industrial robots swap end-of-arm tools (welding torch → gripper → spray gun → grinder) mid-production without stopping the line. Founded 1968 as a Kobe Steel division, spun off independent in 1985; HQ in Kobe, Japan; ~35–40 employees, ~¥1.5–2B revenue — yet claims up to 80% global market share in robot docking systems. Technology: micron-level positioning repeatability, safety locks (tool stays attached even on pressure loss), and media-passing (electricity, pneumatics, hydraulics, water, signals) through the joint — payload classes from a few kilos to automotive body-welding weights; embedded as the de-facto standard by Japanese (Fanuc, Kawasaki, Yaskawa) and European (ABB, KUKA) robot integrators. Diversification from the same precision-mechanics core: inertial gyro sensors (marine, construction) ISO 9001/14001 certified.

Sources

Victim sitetentac.co.jp

Source

Indexed 20 hours 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 868 public disclosures across our corpus. First observed on a leak site on September 9, 2025; most recent post September 15, 2026. The operation is currently active.

Also tracked as: the gentlemen.

Timeline of this disclosure

September 15, 2026Tentac listed by thegentlemen on the group's public leak site

Other recent disclosures by thegentlemen

thegentlemen has been linked to 868 public victims on Darkfield. A sample of the most recent:

See the full thegentlemen dossier →

Sector and geography

This disclosure adds to ransomware activity in the Technology sector, which has 3,577 disclosures indexed across all operators we track. Geographically, Tentac is reported in Japan, a country with 89 ransomware disclosures in our corpus.

If your organisation is affected

A listing by thegentlemen means Tentac 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.
Report the incident to your national CERT, JPCERT/CC (Japan), as required for your jurisdiction.
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.