Attackers increasingly leverage memory-only filesystems (tmpfs) on Linux systems, such as /dev/shm, to conceal malicious tools or stage data for exfiltration. These tmpfs filesystems reside entirely in volatile memory and lack underlying block devices, making traditional forensic imaging tools like dd ineffective for capturing their contents in a forensically sound manner. The described threat centers on the difficulty of collecting forensic evidence from these tmpfs mounts during incident response. The analyst proposes a two-step collection method: first, gather inode metadata using the stat command executed via find, capturing attributes such as inode number, permissions, ownership, size, and timestamps without updating access times. This metadata is formatted in bodyfile format compatible with timeline analysis tools like mactime. Second, collect the actual file contents by finding all regular files and archiving them with tar, compressing the output and transferring it securely to a remote system for analysis. This approach preserves forensic integrity by avoiding timestamp modifications and ensuring comprehensive data capture. The technique has been validated on over a hundred systems, including various Unix-like platforms such as FreeBSD-based Juniper routers and Solaris 9, demonstrating broad applicability. The threat underscores attackers' use of tmpfs to evade detection and complicate forensic investigations, as these in-memory filesystems are ephemeral and not captured by standard disk imaging. While no direct exploit or vulnerability is described, the challenge lies in incident responders' ability to detect and collect evidence from these volatile storage areas. The threat is classified as medium severity due to the requirement of system access for exploitation and the specialized forensic knowledge needed to collect evidence effectively.

For European organizations, especially those operating Linux servers or network devices using tmpfs mounts, this threat complicates incident response and forensic investigations. Attackers can hide malware, scripts, or exfiltration staging data in memory-only filesystems, making detection by traditional disk-based scanning tools ineffective. This can delay detection and remediation, increasing dwell time and potential data loss or system compromise. Critical infrastructure providers, financial institutions, and large enterprises relying on Linux-based systems may face increased risk of stealthy intrusions. The inability to capture tmpfs contents forensically can hinder legal evidence collection and compliance with data breach notification regulations under GDPR. Additionally, organizations with limited incident response expertise or tooling for volatile memory collection may struggle to identify and remediate such threats promptly. Overall, the threat increases the complexity and cost of effective incident response in European environments.

European organizations should enhance their incident response capabilities to include specialized collection techniques for memory-only filesystems. This includes training IR teams on the described two-step method: first collecting inode metadata with stat commands formatted for timeline analysis, then archiving file contents with tar without modifying timestamps. Deploying endpoint detection and response (EDR) tools capable of monitoring tmpfs activity and alerting on suspicious file creation or execution in these mounts can improve detection. Regularly auditing tmpfs usage and restricting write permissions to trusted users can reduce attack surface. Organizations should also integrate volatile memory collection into standard IR playbooks and invest in forensic tooling that supports tmpfs evidence acquisition. Maintaining up-to-date Linux coreutils packages (version 8.32 or later) ensures access to enhanced statx() system calls for better metadata extraction. Finally, segmenting critical systems and applying strict access controls limit attacker ability to write to tmpfs, reducing risk of stealthy payload staging.