The security topic titled "Pentest Trick: Out of sight, out of mind with Windows Long File Names" discusses a penetration testing technique that leverages the behavior of Windows operating systems when handling long file names. Windows supports extended-length paths and file names that can exceed the traditional MAX_PATH limitation (260 characters) by using specific path prefixes (e.g., \\?\). This capability can be exploited by attackers or penetration testers to hide malicious files or payloads in directories or file paths that are difficult to detect or access using standard tools and commands. The technique involves creating files or directories with very long names that may not be fully displayed or indexed by common file explorers, antivirus scanners, or security monitoring tools, effectively making them “out of sight.” This can allow attackers to evade detection, persist on compromised systems, or bypass security controls that do not properly handle or normalize long file paths. Although this is primarily a pentesting trick, it highlights a potential security risk where Windows long file name handling can be abused for stealthy file placement. The discussion is sourced from a Reddit NetSec post linking to an external blog (zerosalarium.com) and has minimal discussion and low Reddit score, indicating limited current awareness or exploitation. No specific affected software versions or CVEs are identified, and no known exploits are reported in the wild. The severity is assessed as medium, reflecting the moderate risk posed by this technique if leveraged by attackers who have some level of access to the system.

For European organizations, this technique could enable attackers who have gained initial access (e.g., via phishing or compromised credentials) to hide malicious files or tools on Windows endpoints or servers. This stealth can delay detection and remediation, increasing dwell time and the potential for data exfiltration, lateral movement, or ransomware deployment. Organizations relying on traditional endpoint detection and response (EDR) tools or antivirus solutions that do not fully support scanning of long file paths may be particularly vulnerable. The impact is more pronounced in environments with extensive Windows infrastructure, including enterprise networks, government agencies, and critical infrastructure sectors. The ability to evade detection can undermine incident response efforts and compliance with European data protection regulations such as GDPR, especially if sensitive data is involved. However, since exploitation requires some level of system access and is not an automatic vulnerability, the overall impact is medium rather than critical.

To mitigate risks associated with abuse of Windows long file names, European organizations should: 1) Ensure endpoint security solutions, including antivirus and EDR tools, are configured and updated to properly scan and detect files with extended-length paths. 2) Implement strict access controls and monitoring to limit the ability of users and processes to create or modify files with unusually long names or paths. 3) Use file integrity monitoring and anomaly detection to identify suspicious file system activity, including creation of hidden or obfuscated files. 4) Educate security teams and system administrators about this technique to improve detection capabilities during incident investigations. 5) Employ PowerShell and scripting tools that can handle long paths to audit and clean up suspicious files. 6) Regularly review and harden Windows file system policies and group policies to restrict unnecessary file system operations. 7) Incorporate this knowledge into penetration testing and red team exercises to validate detection and response readiness. These measures go beyond generic advice by focusing on the specific challenge of long file path handling and detection.