Was Kobayashi hit by ransomware?

Kobayashi was listed by the worldleaks 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 worldleaks ransomware group?

worldleaks 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 Kobayashi breach?

worldleaks published data attributed to Kobayashi. Darkfield captured the leak post and a screenshot of the listing.

Ransomware victim disclosure

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Kobayashi & Co., Ltd.

listed as Kobayashi · Claimed by Worldleaks · listed 9 months ago

Age

since listed · data leaked

Status timeline

ListedNov 1, 2025
Data leakeddate unknown

At a glance

Group: Worldleaks
Status: Data leaked
Country: Japan
Listed on leak site: Nov 1, 2025

About the victim

AI dossier — public-source company profile

Kobayashi & Co., Ltd. (株式会社コバヤシ) is a Japanese plastics integrated company operating as both a trading company and manufacturer. It supplies a wide range of plastic products across five business divisions including containers, industrial materials, distribution materials, and new product development. The company also develops sustainable materials such as biomass-blended plastics under its proprietary 'Reseam®' brand.

Industry: Plastics Manufacturing & Distribution

Attack summary

Severity: medium — Data is stated as published (disclosed status: data_published), indicating exfiltration occurred, but no data size, data type inventory, or proof files are described, and the leak post content appears AI-generated with no verified specifics about the actual stolen data.

The worldleaks group claims to have published data belonging to Kobayashi & Co., Ltd., with the disclosure status recorded as data_published. The leak post content was AI-generated and incorrectly describes a different company (Kobayashi Pharmaceutical), suggesting limited verified detail about the actual exfiltrated data.

medium

Original description

AI-summarised, not from the leak post

Kobayashi Pharmaceutical Co. Ltd. is a Japanese company that specializes in the manufacturing and sale of over-the-counter drugs, oral hygiene products, and healthcare items. Their extensive product line-up includes cool fever patches, pain relief patches, skin creams, oral care products, and other health-related goods garnering a global presence. They focus on enhancing everyday health and comfort for their customers.

Sources

Victim sitewww.kbjapan.co.jp
Leak posthttps://worldleaksartrjm3c6vasllvgacbi5u3mgzkluehrzhk2jz4taufuid.onion/companies/5218015704

Source

Indexed 9 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 worldleaks

Based on the limited available data, worldleaks is a recently emerged ransomware group that was first observed in May 2025 and appears to be primarily financially motivated, having claimed 134 victims in a relatively short timeframe since its emergence. The group's origin and organizational structure remain unclear, with no publicly documented information from major cybersecurity firms or law enforcement agencies regarding their country of origin, potential affiliations, or operational model. Their targeting patterns indicate a focus on English-speaking countries, particularly the United States, United Kingdom, and Canada, with additional activity observed in Germany and Japan, while their sector targeting shows a preference for healthcare, technology, manufacturing, and consumer services organizations. Due to the group's recent emergence and limited public documentation by established threat intelligence sources, specific details about their attack methodologies, encryption techniques, extortion tactics, and notable campaigns have not yet been comprehensively analyzed or reported by organizations such as CISA, FBI, or major cybersecurity research firms. The group appears to remain active as of the most recent observations, though comprehensive threat intelligence profiling awaits further analysis and documentation by established cybersecurity authorities. The group has been linked to 173 public disclosures across our corpus. First observed on a leak site on May 18, 2025; most recent post July 2, 2026. The operation is currently active.

Timeline of this disclosure

November 1, 2025Kobayashi listed by worldleakson the group's public leak site

Other recent disclosures by worldleaks

worldleaks has been linked to 173 public victims on Darkfield. A sample of the most recent:

See the full worldleaks dossier →

Sector and geography

Geographically, Kobayashi is reported in Japan, a country with 220 ransomware disclosures in our corpus.

If your organisation is affected

A listing by worldleaks means Kobayashi 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 worldleaks'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.