The New FileFix attack is a recently identified campaign that leverages JScript execution to bypass Windows Mark of the Web (MoTW) security alerts. MoTW is a security feature in Windows that tags files downloaded from the internet with metadata indicating their origin, triggering warnings or restrictions when users attempt to open or execute these files. This attack circumvents these alerts, allowing malicious JScript code to run without raising the usual security prompts that would warn users of potential risk. By evading MoTW, attackers can execute scripts that may download additional payloads, perform reconnaissance, or establish persistence on the victim's system. The attack does not rely on exploiting a specific software vulnerability but instead abuses the way Windows handles script execution and security markings. Although no specific affected software versions or patches are currently identified, the technique targets Windows environments where MoTW is active and JScript execution is permitted. The campaign is considered high severity due to its ability to bypass a fundamental security control designed to protect users from executing potentially harmful files originating from untrusted sources. While there are no known exploits in the wild at the time of reporting, the minimal discussion and recent discovery suggest that this threat could evolve rapidly, especially if threat actors adopt this technique to deliver malware or ransomware payloads.

For European organizations, this threat poses a significant risk as it undermines a core security mechanism in Windows environments widely used across enterprises. The ability to silently execute malicious scripts without triggering MoTW alerts increases the likelihood of successful initial compromise, lateral movement, and deployment of secondary payloads such as ransomware or data exfiltration tools. Organizations relying on Windows-based endpoints and lacking advanced script execution controls or endpoint detection capabilities may find it difficult to detect or prevent this attack. The stealthy nature of the attack could lead to prolonged undetected breaches, impacting confidentiality, integrity, and availability of critical systems. Given the prevalence of Windows in European corporate networks and the increasing targeting of European entities by cybercriminal groups, this attack vector could facilitate disruptive campaigns affecting sectors such as finance, healthcare, manufacturing, and government institutions.

To mitigate this threat, European organizations should implement several targeted measures beyond generic advice: 1) Enforce strict execution policies for scripts using Group Policy or AppLocker to restrict JScript and other scripting languages to trusted locations or signed scripts only. 2) Enhance endpoint detection and response (EDR) solutions to monitor for unusual script execution patterns and bypass attempts of MoTW alerts. 3) Disable or limit Windows Script Host (WSH) where not required, reducing the attack surface for script-based attacks. 4) Employ network-level controls to detect and block command and control traffic typically associated with script-based payloads. 5) Conduct user awareness training focused on the risks of executing files from untrusted sources despite the absence of security warnings. 6) Regularly audit and update security configurations related to file execution policies and Windows security features to ensure no gaps exist that could be exploited by this technique. 7) Monitor threat intelligence feeds for updates on this campaign and apply any forthcoming patches or vendor recommendations promptly.