The Qilin ransomware group has recently adopted a new tactic involving a custom stealer to target and harvest account credentials stored in Google Chrome. This change was observed by the Sophos X-Ops team during incident response engagements and represents a significant shift in ransomware strategies. The attack begins with Qilin gaining access to a network through compromised VPN credentials that lacked multi-factor authentication (MFA). After an initial period of dormancy, the attackers used this time for reconnaissance and network mapping.
Following the reconnaissance phase, Qilin moved laterally to a domain controller and altered Group Policy Objects (GPOs) to deploy a PowerShell script across all domain-connected machines. This script, executed via a batch file on user logins, was designed to collect stored Chrome credentials. These stolen credentials were saved on a shared network location and then exfiltrated to Qilin’s command and control server, while local copies and event logs were deleted to avoid detection.
The approach taken by Qilin, involving credential harvesting from Chrome, poses a significant risk to organizations as it facilitates extensive and undetected data theft. Since the GPO was applied to all domain machines, any device used during the attack was susceptible to credential theft, potentially leading to widespread breaches. This method not only complicates the response process but also leaves a persistent threat that requires extensive remediation efforts, including changing passwords across multiple platforms.
To defend against such attacks, organizations are advised to implement strict policies against storing credentials in web browsers and enforce multi-factor authentication to protect accounts. Network segmentation and the principle of least privilege are also crucial in limiting the spread of threats within compromised networks. Given the evolving tactics of Qilin, which has connections to social engineering experts like Scattered Spider, the threat landscape continues to grow more complex and challenging.
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