Linux: Potential Data Exfiltration via Wget Utility

Data exfiltration activity on Linux systems is often conducted by staging files in directories such as /tmp and utilizing the wget utility to push these files to remote servers via HTTP POST requests. This activity frequently originates from non-interactive shell sessions or automated tasks like cron jobs. While wget is a legitimate networking tool, the use of upload-specific flags when interacting with external web resources is highly suspicious and warrants immediate investigation.

Attack Chain

1. Collection: The attacker identifies and accesses sensitive data, such as credentials, configuration files, or user archives.
2. Staging: Collected files are compressed or moved to a directory, commonly /tmp, /var/tmp, or user home directories, to prepare for exfiltration.
3. Execution: The attacker initiates an outbound connection using wget with POST-capable flags (e.g., --post-file, --body-file).
4. Exfiltration: Data is transmitted via HTTP/HTTPS to an external command-and-control server.

Impact

Unauthorized exfiltration of sensitive information, including credentials, source code, and customer data, potentially leading to long-term persistence, further network compromise, or data exposure.

Recommendation

• Deploy detection rules to identify suspicious execution of wget with file-upload arguments.
• Audit cron jobs, systemd services, and scheduled tasks to identify unauthorized scripts containing wget upload commands.
• Implement egress filtering to restrict HTTP POST requests to known, approved destinations.
• Restrict the execution of wget to only authorized users and processes via filesystem permissions or application allowlisting.