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Cyber Threat
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Ransomware victim Manufacturing

Mutsumi Group

Listed by Qilin on · organisation based in Japan

www.mutsumi-g.co.jp

Disclosed
Oct 4, 2026
Leak-site listing date
Threat group
Qilin
2,385 victims listed
Country
Japan
#11 most targeted
Sector
Manufacturing

ThreatAI analysis

Compiled from this incident record and the threat intelligence profile for Qilin. Figures and technique mappings are quoted from the source data, not inferred.

Mutsumi Group was listed on Qilin's dark web leak site on 4 October 2026; the group is based in Japan and operates in the Manufacturing sector.

About the Qilin group

Qilin ransomware was first observed in July of 2022. Qilin Ransomware is written in Golang and supports multiple encryption modes; all of which are controlled by the operator. Qilin actors practice double extortion – demanding payment for a decryptor, as well as for the non-release of stolen data. Qilin has listed 2,344 victims since October 2022.

How Qilin is documented to operate

Valid Accounts T1078 Stealth Persistence

Adversaries may obtain and abuse credentials of existing accounts as a means of gaining Initial Access, Persistence, Privilege Escalation, or Defense Evasion. Compromised credentials may be used to bypass access controls placed on various resources on systems within the network and may even be used for persistent access to remote systems and externally available services, such as VPNs, Outlook Web Access, network devices, and remote desktop. Compromised credentials may also grant an adversary increased privilege to specific systems or access to restricted areas of the network.

Mitigations: Application Developer Guidance, User Training, Password Policies, User Account Management, Privileged Account Management, Multi-factor Authentication

MITRE ATT&CK reference
Exploit Public-Facing Application T1190 Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network. The weakness in the system can be a software bug, a temporary glitch, or a misconfiguration. Exploited applications are often websites/web servers, but can also include databases (like SQL), standard services (like SMB or SSH), network device administration and management protocols (like SNMP and Smart Install), and any other system with Internet-accessible open sockets. On ESXi infrastructure, adversaries may exploit exposed OpenSLP services; they may alternatively exploit exposed VMware vCenter servers.

Mitigations: Vulnerability Scanning, Limit Access to Resource Over Network, Filter Network Traffic, Network Segmentation, Privileged Account Management, Application Isolation and Sandboxing

MITRE ATT&CK reference
Phishing T1566 Initial Access

Adversaries may send phishing messages to gain access to victim systems. All forms of phishing are electronically delivered social engineering. Phishing can be targeted, known as spearphishing. In spearphishing, a specific individual, company, or industry will be targeted by the adversary. More generally, adversaries can conduct non-targeted phishing, such as in mass malware spam campaigns. Adversaries may send victims emails containing malicious attachments or links, typically to execute malicious code on victim systems. Phishing may also be conducted via third-party services, like social media platforms.

Mitigations: Network Intrusion Prevention, Restrict Web-Based Content, User Training, Antivirus/Antimalware, Software Configuration, Audit

MITRE ATT&CK reference

MITRE ATT&CK techniques attributed to Qilin across its recorded activity, not a finding about how Mutsumi Group was reached.

Vulnerabilities Qilin is recorded exploiting

5 of these 6 are in the CISA Known Exploited Vulnerabilities catalog, 4 of them recorded by CISA as used in ransomware campaigns. CVEs attributed to Qilin across its reported activity. There is no indication that any of these was involved in the Mutsumi Group incident — the source data does not record an entry point.

Incident analysis

Mutsumi Group was listed by Qilin ransomware, a group with 2,385 victims recorded in this database. The listing appeared on the group's leak site on October 4, 2026.

Mutsumi Group is based in Japan and operates in the Manufacturing sector. Japan ranks #11 worldwide for ransomware disclosures, with 294 victims in this database.

Sector context. Manufacturing companies are frequently targeted because production downtime directly translates to financial loss. Ransomware operators exploit this time-sensitivity to demand higher ransoms and faster payment.

Qilin typically follows a double extortion model: data is exfiltrated from the victim's systems before files are encrypted, so the victim faces two demands at once — pay to restore access, and pay to keep stolen data unpublished. The leak site, where this listing appeared, is the lever for the second demand.

Source. Public leak-site disclosures aggregated via the ransomware.live API. The disclosure date is when the listing was published, which can differ from the date of compromise. This site does not publish or link to stolen data. Last updated .

Frequently asked questions

Was Mutsumi Group attacked by ransomware?

Yes. Mutsumi Group was listed as a victim of the Qilin ransomware group on October 4, 2026. The organisation is based in Japan and operates in the Manufacturing sector. The disclosure appeared on the group's dark web leak site.

Which ransomware group attacked Mutsumi Group?

Mutsumi Group was attacked by Qilin ransomware. Qilin is one of the most active ransomware groups, having claimed 2,385 victims globally. The group typically employs a double-extortion model: encrypting the victim's files and threatening to publish stolen data.

When did the Mutsumi Group ransomware attack occur?

The ransomware attack on Mutsumi Group was disclosed on October 4, 2026. This date reflects when the victim was published on the threat group's leak site, which may differ from the actual date of initial compromise.

What data was stolen in the Mutsumi Group ransomware attack?

The specific data stolen from Mutsumi Group has not been independently verified by this platform. Ransomware groups typically exfiltrate data before encrypting systems and use the threat of publication to pressure victims. As a Manufacturing organisation, Mutsumi Group likely held sensitive business data, client information, and operational records.

How can organisations protect against Qilin attacks?

To defend against Qilin and similar threat actors, organisations should: maintain regular offline backups tested for restoration; implement network segmentation to limit lateral movement; deploy multi-factor authentication on all remote access; use endpoint detection and response (EDR) tools; conduct regular phishing and security awareness training; and monitor threat intelligence feeds for indicators of compromise (IOCs) associated with active groups.