Qilin Ransomware Turns South Korean MSP Breach Into 28-Victim 'Korean Leaks' Data Heist
Summary:
Bitdefender’s investigation into ransomware activity for the October 2025 Threat Debrief uncovered an unexpected anomaly: South Korea suddenly became the second most-impacted country globally, with 25 victims recorded in a single month. This surge stood out against long-established ransomware patterns and prompted a deeper review. Bitdefender’s analysis determined that the entire spike originated from a single operation by the Qilin Ransomware-as-a-Service group. Nearly all of the affected organizations were financial and asset-management firms, indicating a highly targeted campaign rather than random victim selection. Qilin released stolen data across three organized publication waves under the branding “Korean Leaks,” sharing proof-of-compromise photos and partial file counts that confirmed theft of more than one million documents and multiple terabytes of data.
In addition to identifying Qilin as the operator, Bitdefender analyzed the messaging, timing, and structure of the campaign, noting the unusual political tone used in many of the leak-site posts. The publication patterns and earlier Qilin communications aligned with a possible collaboration between Qilin and a North Korean-linked affiliate, Moonstone Sleet, which had previously experimented with Qilin ransomware. Bitdefender also examined multiple hypotheses for how the attackers gained such broad access to one industry. The technical review pointed toward a shared upstream dependency, and this was confirmed by South Korean press reporting that a domestic Managed Service Provider supporting numerous asset-management firms had been compromised. Bitdefender concluded that the “Korean Leaks” operation was enabled by that single MSP intrusion, which allowed attackers to reach dozens of interconnected financial organizations in a short period, ultimately driving the unusual ransomware spike observed in the monthly statistics.
Security Officer Comments:
The Korean Leaks campaign highlights how rapidly threat actors can scale operations when an upstream service provider is compromised, reinforcing that MSP intrusions remain one of the most effective ways to mass-access tightly clustered industries. Qilin’s role as the operator and publisher is clear, but the style, timing, and political overtones in the leak-site messaging point to an affiliate with distinct motivations—consistent with Moonstone Sleet’s previous experimentation with Qilin ransomware. This blending of state-linked actors with a mature RaaS ecosystem reflects an accelerating trend: nation-state groups adopting criminal platforms to mask attribution, diversify revenue streams, and amplify geopolitical narratives.
Suggested Corrections:
Backup your data, system images, and configurations, regularly test them, and keep the backups offline: Ensure that backups are regularly tested and that they are not connected to the business network, as many ransomware variants try to find and encrypt or delete accessible backups. Maintaining current backups offline is critical because if your network data is encrypted with ransomware, your organization can restore systems.
Update and patch systems promptly: This includes maintaining the security of operating systems, applications, and firmware in a timely manner. Consider using a centralized patch management system; use a risk-based assessment strategy to drive your patch management program.
Test your incident response plan: There's nothing that shows the gaps in plans more than testing them. Run through some core questions and use those to build an incident response plan: Are you able to sustain business operations without access to certain systems? For how long? Would you turn off your manufacturing operations if business systems such as billing were offline?
Check your security team's work: Use a 3rd party pen tester to test the security of your systems and your ability to defend against a sophisticated attack. Many ransomware criminals are aggressive and sophisticated and will find the equivalent of unlocked doors.
Segment your networks: There's been a recent shift in ransomware attacks – from stealing data to disrupting operations. It's critically important that your corporate business functions and manufacturing/production operations are separated and that you carefully filter and limit internet access to operational networks, identify links between these networks, and develop workarounds or manual controls to ensure ICS networks can be isolated and continue operating if your corporate network is compromised. Regularly test contingency plans such as manual controls so that safety-critical functions can be maintained during a cyber incident.
Train employees: Email remains the most vulnerable attack vector for organizations. Users should be trained on how to avoid and spot phishing emails.
Implement multi-factor authentication (MFA): External-facing assets that leverage single-factor authentication (SFA) are highly susceptible to brute-forcing attacks, password spraying, or unauthorized remote access using valid (stolen) credentials. Implementing MFA enhances security and adds an extra layer of protection.
Link(s):
https://www.bitdefender.com/en-us/b...th-korean-financial-services-qilin-ransomware
Bitdefender’s investigation into ransomware activity for the October 2025 Threat Debrief uncovered an unexpected anomaly: South Korea suddenly became the second most-impacted country globally, with 25 victims recorded in a single month. This surge stood out against long-established ransomware patterns and prompted a deeper review. Bitdefender’s analysis determined that the entire spike originated from a single operation by the Qilin Ransomware-as-a-Service group. Nearly all of the affected organizations were financial and asset-management firms, indicating a highly targeted campaign rather than random victim selection. Qilin released stolen data across three organized publication waves under the branding “Korean Leaks,” sharing proof-of-compromise photos and partial file counts that confirmed theft of more than one million documents and multiple terabytes of data.
In addition to identifying Qilin as the operator, Bitdefender analyzed the messaging, timing, and structure of the campaign, noting the unusual political tone used in many of the leak-site posts. The publication patterns and earlier Qilin communications aligned with a possible collaboration between Qilin and a North Korean-linked affiliate, Moonstone Sleet, which had previously experimented with Qilin ransomware. Bitdefender also examined multiple hypotheses for how the attackers gained such broad access to one industry. The technical review pointed toward a shared upstream dependency, and this was confirmed by South Korean press reporting that a domestic Managed Service Provider supporting numerous asset-management firms had been compromised. Bitdefender concluded that the “Korean Leaks” operation was enabled by that single MSP intrusion, which allowed attackers to reach dozens of interconnected financial organizations in a short period, ultimately driving the unusual ransomware spike observed in the monthly statistics.
Security Officer Comments:
The Korean Leaks campaign highlights how rapidly threat actors can scale operations when an upstream service provider is compromised, reinforcing that MSP intrusions remain one of the most effective ways to mass-access tightly clustered industries. Qilin’s role as the operator and publisher is clear, but the style, timing, and political overtones in the leak-site messaging point to an affiliate with distinct motivations—consistent with Moonstone Sleet’s previous experimentation with Qilin ransomware. This blending of state-linked actors with a mature RaaS ecosystem reflects an accelerating trend: nation-state groups adopting criminal platforms to mask attribution, diversify revenue streams, and amplify geopolitical narratives.
Suggested Corrections:
Backup your data, system images, and configurations, regularly test them, and keep the backups offline: Ensure that backups are regularly tested and that they are not connected to the business network, as many ransomware variants try to find and encrypt or delete accessible backups. Maintaining current backups offline is critical because if your network data is encrypted with ransomware, your organization can restore systems.
Update and patch systems promptly: This includes maintaining the security of operating systems, applications, and firmware in a timely manner. Consider using a centralized patch management system; use a risk-based assessment strategy to drive your patch management program.
Test your incident response plan: There's nothing that shows the gaps in plans more than testing them. Run through some core questions and use those to build an incident response plan: Are you able to sustain business operations without access to certain systems? For how long? Would you turn off your manufacturing operations if business systems such as billing were offline?
Check your security team's work: Use a 3rd party pen tester to test the security of your systems and your ability to defend against a sophisticated attack. Many ransomware criminals are aggressive and sophisticated and will find the equivalent of unlocked doors.
Segment your networks: There's been a recent shift in ransomware attacks – from stealing data to disrupting operations. It's critically important that your corporate business functions and manufacturing/production operations are separated and that you carefully filter and limit internet access to operational networks, identify links between these networks, and develop workarounds or manual controls to ensure ICS networks can be isolated and continue operating if your corporate network is compromised. Regularly test contingency plans such as manual controls so that safety-critical functions can be maintained during a cyber incident.
Train employees: Email remains the most vulnerable attack vector for organizations. Users should be trained on how to avoid and spot phishing emails.
Implement multi-factor authentication (MFA): External-facing assets that leverage single-factor authentication (SFA) are highly susceptible to brute-forcing attacks, password spraying, or unauthorized remote access using valid (stolen) credentials. Implementing MFA enhances security and adds an extra layer of protection.
Link(s):
https://www.bitdefender.com/en-us/b...th-korean-financial-services-qilin-ransomware