How To Create a Secure FTP Server with Linux and SSH

FTP (File Transfer Protocol) remains an invaluable component of the business technology landscape for those not quite adept at running an entire build system. While going full cloud may seem appealing, think twice if any files that contain sensitive information need to be uploaded and downloaded through third-party services without your control.

It is crucial to ensure that files are uploaded securely and reliably, and sometimes, that means keeping them within your local area network (LAN). Luckily, as always, Linux has your back. Secure Shell (SSH) makes setting up an FTP server more straightforward than ever. Once set up, files can be moved between servers using Secure FTP for reliable information transmission. SFTP (or Secure File Transfer Protocol) is an alternative to FTP for transferring files, adding a layer of security to the process.

Today, I'm sharing an awesome tutorial on how to set up a Secure File Transfer Protocol (SFTP) to move files around your Linux servers (linked at the end of this article. But first, let's examine the security implications and considerations regarding FTP and SFTP that you should be familiar with before proceeding.

FTP Security Implications & Considerations

There are various security considerations and implications admins should be familiar with regarding FTP:

• Transmission in Clear Text: FTP does not encrypt its traffic; all transmissions, including login credentials, are made in plain text and thus vulnerable to interception and eavesdropping by third parties. Using FTP over an unprotected network is considered risky regarding Linux security.
• Secure Alternatives: For secure file transfers, protocols like SFTP (SSH File Transfer Protocol) or FTPS (FTP Secure, an extension of FTP with TLS security) should be utilized. SFTP, in particular, integrates seamlessly with SSH (Secure Shell) and provides encrypted channels that offer authentication and data transfer services.
• Firewall Configuration: Setting up firewalls to permit FTP traffic can be complex due to its use of multiple ports and, in active mode, random connections from various clients to random ports on their client systems. Proper firewall configuration is crucial in protecting any Linux system requiring FTP access.
• User Isolation: Implementing user isolation on FTP servers is essential to prevent authenticated users from accessing unauthorized files, which involves configuring the FTP server to restrict users to specific directories and enforce permission settings.
• Regular Updates and Audits: Keeping FTP server software current is crucial to protecting against vulnerabilities, so regular security audits should also be undertaken to protect against potential issues.

FTP is a popular protocol for file transfers, yet its lack of security features renders it less appropriate when transmitting sensitive information across insecure networks. Linux environments prioritize data confidentiality and integrity and often prefer alternatives like SFTP or FTPS as the transfer protocols for data transmission.

What Makes SFTP More Secure than FTP?

SFTP is a more secure alternative to FTP for the following reasons:

• Encryption: SFTP uses the SSH protocol to encrypt data in transit. This means all data, including passwords, files, and commands, are transmitted securely.
• Authentication: SFTP supports more robust and versatile authentication mechanisms, including passwords, public keys, or a combination of methods. This multi-factor authentication significantly improves security.
• Single Connection: SFTP uses a single, secure connection for commands and data transfer (over SSH), simplifying the setup. With SFTP, handling multiple ports is unnecessary, which reduces the attack surface.
• Integrity and Confidentiality: Because it transmits data securely via encrypted packets, SFTP ensures that unauthorized parties cannot easily view or modify data during transmission.

Next Steps: Setting Up an SFTP on Linux

Due to its secure nature, SFTP is recommended over FTP in almost all cases involving the transmission of sensitive or confidential information.

To get started with SFTP, I encourage you to explore the tutorial linked below to learn how to set up a Secure File Transfer Protocol (SFTP) to move files around your Linux servers.