Disclosure context

About beast

The Beast ransomware group is a relatively new threat actor that emerged in July 2025, operating with apparent financial motivations through their ransomware campaigns. With limited public documentation available from major security agencies, the group has demonstrated activity primarily targeting victims across the United States, United Kingdom, Brazil, South Korea, and Argentina, accumulating approximately 65 known victims since their emergence. Their targeting pattern shows a focus on healthcare organizations, manufacturing companies, educational institutions, and construction firms, suggesting an opportunistic approach rather than highly specialized sector expertise. The group's recent emergence means there is insufficient public intelligence from CISA, FBI, Mandiant, or other established security researchers regarding their specific attack methodologies, initial access vectors, or technical capabilities. Given the timeline of their first observation in mid-2025, Beast represents an active and emerging threat with their current operational status remaining unclear due to limited threat intelligence reporting from authoritative sources. The group has been linked to 75 public disclosures across our corpus. First observed on a leak site on July 29, 2025; most recent post May 21, 2026. The operation is currently active.

Timeline of this disclosure

February 5, 2026Yulkok Ltd listed by beaston the group's public leak site

Sector and geography

This disclosure adds to ransomware activity in the Not Found sector, which has 4,859 disclosures indexed across all operators we track. Geographically, Yulkok Ltd is reported in South Korea, a country with 32 ransomware disclosures in our corpus.

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.

Ransomware victim disclosure

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Yulkok Ltd

Claimed by beast · listed 3 months ago

Age

since listed · data leaked

Status timeline

Listed
Feb 5, 2026
Data leaked

At a glance

Group: beast
Status: Data leaked
Country: South Korea
Sector: Not Found
Listed on leak site: Feb 5, 2026

About the victim

AI dossier — public-source company profile

Yulkok Ltd. is a South Korean aerospace manufacturer headquartered in Changwon, founded in 1990. The company specialises in high-precision 5-axis CNC metal machining and fuselage component assembly for the aerospace industry. It supplies components to major global customers including Boeing, Airbus, and Korea Aerospace Industries (KAI), including for military aircraft such as the T-50 and FA-50.

Industry: Aerospace & Defence Manufacturing
Address: Changwon, South Korea
Founded: 1990

Attack summary

Severity: critical — Yulkok Ltd. is an aerospace and defence manufacturer producing components for military aircraft (T-50, FA-50) in partnership with Boeing, Airbus, and KAI. Data published from such a firm is highly likely to include sensitive defence-related technical data, manufacturing specifications, and potentially export-controlled information, placing this in the critical category.

The BEAST ransomware group claims to have attacked Yulkok Ltd. and has published data ('data_published' status), though the leak post does not specify whether encryption, exfiltration, or both occurred, nor the volume of data involved.

critical

Data the group says was taken

AI dossier — extracted from the leak post

Aerospace manufacturing data
Defence component specifications
Partner/supplier information

What the group claims

Yulkok Ltd. (South Korea) This is a major global player with the same name. Operations: Manufacturing high-precision parts and assemblies for the aerospace industry. Specialization: 5-axis CNC metal machining, fuselage component assembly. Partners: Collaborates with global giants such as Boeing and Airbus, as well as Korea Aerospace Industries (KAI) for the production of military aircraft (e.g., T-50, FA-50). Location: Headquartered in Changwon, South Korea; founded in 1990.

The leak post

captured from the group's site

AJU Pharm Co., Ltd. is a prominent South Korean total healthcare company founded in 1953. For over 70 years, it has evolved from a manufacturer of raw materials into a global pharmaceutical group specializing in prescription drugs, medical devices, and health supplements
P U B L I S H E D

Sources

Victim sitewww.yulkok.com
Leak posthttp://beast6azu4f7fxjakiayhnssybibsgjnmy77a6duufqw5afjzfjhzuqd.onion/card/yulkok_ltd

Source

Indexed 3 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.