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Researchers have uncovered a new and sophisticated variant of the Interlock RAT, a remote access trojan associated with the Interlock ransomware group. This latest iteration is written in PHP, marking a departure from previously observed JavaScript-based versions. The malware is being distributed through a widespread campaign that leverages compromised websites and Cloudflare tunnels. The attack chain begins with a single-line script injected into website HTML, often unbeknownst to the website owners. This script employs IP filtering to serve the payload, which then manipulates the user into clicking a captcha for "verification," ultimately leading to the execution of a PowerShell script that deploys the Interlock RAT.
The delivery mechanism for this new PHP variant utilizes the KongTuke FileFix technique. Researchers have noted that this updated method has been observed deploying the PHP version of the Interlock RAT, and in some instances, this has subsequently led to the deployment of the Node.js variant of the same RAT. The capabilities of this Interlock RAT variant include remote control of compromised systems, thorough system reconnaissance, and the ability to perform lateral movement within a network. This demonstrates an evolving level of sophistication in the threat actor's tactics.
The DFIR Report, in collaboration with Proofpoint, identified the malware and its distribution methods. The observed execution involves a PowerShell command that deletes a scheduled task named "Updater" before downloading and executing a script from a specific URL. This script, in turn, abuses the `php.exe` executable from an uncommon location to further download and execute the RAT. Security professionals are advised to be aware of PowerShell spawning `php.exe` from unusual directories as a potential indicator of compromise. Additionally, the RAT's reconnaissance activities, such as running `systeminfo`, `tasklist`, `whoami`, or `nltest`, provide further opportunities for detection.
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Classification:
- HashTags: #InterlockRAT #KongTuke #Malware
- Company: Interlock
- Target: Websites
- Attacker: The DFIR Report
- Product: FileFix
- Feature: RAT
- Malware: Interlock RAT
- Type: Malware
- Severity: Major