The KongTuke FileFix represents a newly identified variant of the Interlock ransomware group’s remote access trojan (RAT), marking a significant evolution in their malware toolkit. Previously, the Interlock RAT, also known as NodeSnake, was primarily JavaScript-based, but this new variant is implemented in PHP. This shift in programming language suggests an adaptation to evade detection and potentially target different environments, particularly those running PHP-based web applications or servers. The malware is part of a widespread campaign, indicating active and ongoing operations by the threat actors. The use of PHP could allow the malware to blend into web server environments more seamlessly, leveraging common web technologies to maintain persistence and facilitate command and control communications. Although no specific affected software versions or exploits have been disclosed, the campaign’s scale and the malware’s resilience highlight a sophisticated threat actor capable of evolving their tactics. The absence of known exploits in the wild suggests this variant may be newly deployed or under active development, but its association with ransomware groups implies a high risk of data encryption and extortion activities. The technical details emphasize that the information was sourced from a Reddit NetSec post linked to The DFIR Report and Proofpoint research, lending credibility to the findings despite limited public discussion. Overall, this threat represents a notable advancement in ransomware-associated RAT capabilities, leveraging PHP to potentially increase stealth and effectiveness in compromising targeted systems.

For European organizations, the emergence of the KongTuke FileFix PHP-based Interlock RAT variant poses several risks. Organizations running PHP-based web servers, content management systems (CMS), or custom web applications are particularly vulnerable, as the malware could exploit common web hosting environments prevalent across Europe. Successful compromise could lead to unauthorized remote access, data exfiltration, and deployment of ransomware payloads, resulting in operational disruption, financial loss, and reputational damage. Critical infrastructure, healthcare, education, and government sectors in Europe, which often rely on web-facing applications, could be targeted to maximize impact. The campaign’s widespread nature increases the likelihood of European entities encountering this threat, especially those with less mature cybersecurity defenses or outdated PHP environments. Additionally, the malware’s resilience and adaptability could complicate detection and incident response efforts, prolonging recovery times and increasing costs. The potential for ransomware deployment further elevates the threat, as encrypted data and ransom demands can severely disrupt business continuity and critical services. Given the evolving tactics of the Interlock group, European organizations must remain vigilant against this emerging threat vector.

To mitigate the risks posed by the KongTuke FileFix Interlock RAT variant, European organizations should implement targeted and proactive measures beyond generic advice. First, conduct comprehensive audits of all PHP-based web applications and servers to identify and remediate vulnerabilities, including outdated PHP versions and unpatched CMS platforms. Employ application-layer firewalls and intrusion detection systems specifically tuned to detect anomalous PHP scripts and unusual outbound traffic patterns indicative of RAT activity. Implement strict access controls and network segmentation to limit lateral movement if a web server is compromised. Regularly monitor logs for suspicious PHP execution and command and control communication attempts. Employ threat hunting focused on indicators of compromise related to Interlock RAT behaviors, even if specific IOCs are not yet public. Backup critical data with immutable and offline copies to ensure recovery in case of ransomware encryption. Educate development and IT teams on secure coding practices and the risks of PHP-based malware. Finally, collaborate with threat intelligence sharing communities to stay updated on emerging indicators and tactics associated with this campaign.