Fortinet/FortiGuard Labs reported that the Interlock ransomware group—described as a smaller, non-RaaS operation—ran a months-long intrusion campaign primarily targeting the education sector in the US and UK. Initial access was observed via MintLoader, including “ClickFix” social-engineering lures, followed by post-compromise activity using a JavaScript implant referred to as NodeSnakeRAT, lateral movement with valid accounts and living-off-the-land techniques, and broad discovery prior to impact. The operation follows a double-extortion pattern, with data exfiltration (including use of AZcopy) preceding ransomware deployment, and has been observed impacting both Windows endpoints and Nutanix hypervisor environments.
A key technical finding is Interlock’s use of a Bring Your Own Vulnerable Driver (BYOVD) technique to neutralize endpoint defenses. Researchers identified a custom tool dubbed “Hotta Killer” (associated with polers.dll) that drops a kernel driver UpdateCheckerX64.sys, described as a renamed vulnerable anti-cheat driver (GameDriverx64.sys, CVE-2025-61155). Because the driver is legitimate and digitally signed, it can pass initial trust checks; once loaded, it is abused for kernel-level process termination to kill EDR/AV processes, with reporting noting targeting of Fortinet security tooling specifically, enabling subsequent ransomware execution with reduced detection and response capability.

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Fortinet publicly reported that Interlock used a custom EDR/AV killer called Hotta Killer, which exploited a zero-day in the signed anti-cheat driver GameDriverx64.sys via a BYOVD technique. The flaw was tracked as CVE-2025-61155 and was used to terminate security software, including Fortinet products, at kernel level.
Following the start of encryption, the attackers generated roughly 5,000 rogue domain user accounts. The purpose was unclear, but FortiGuard suggested it may have been intended to create confusion or hinder incident response.
On October 10, 2025, Interlock began encryption using a Linux encryptor against Nutanix servers and a JavaScript payload called jar.jar against Windows endpoints. The operation affected both hypervisor and endpoint environments.
By September 2025, the attackers had escalated the intrusion by exfiltrating more than 250 GB of data using AZcopy to cloud storage. This activity supported the group's double-extortion model before encryption was launched.
After initial access, Interlock deployed a custom JavaScript implant known as NodeSnake RAT to maintain long-term access and support lateral movement using valid accounts and living-off-the-land techniques.
FortiGuard Labs reported that an Interlock ransomware intrusion against the education sector began with a MintLoader infection, likely delivered through ClickFix social engineering. The campaign targeted education organizations in the U.S. and U.K.
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