SFTP Security: How to Secure File Transfers with SFTP

SFTP Security: How to Secure File Transfers with SFTP. SFTP (Secure File Transfer Protocol) is a commonly used protocol for sharing files between computers. It is based on the FTP protocol, but it includes SSH(Secure Shell) security features. With SFTP, you securely transfer encrypted files from a client to a server and vice versa without worrying about attacks while on transit.

However, while SFTP aims to provide security, there are numerous measures to take to improve security. This article discusses various ways on how to secure file transfers with SFTP. Read on!

SFTP Security: 10 ways to Secure File Transfers with SFTP

1. Disable FTP

Most SFTP clients and servers come with the FTP functionality. It’s crucial to disable it as you might confuse and use it over SFTP. FTP is a quite outdated protocol that lacks the security features of modern protocols. Unlike SFTP, FTP sends data without any security, making it vulnerable to attacks. By disabling FTP on your server, you remove a potential attack vector. 

Why don’t you move data to the more secure  FTPS (File Transfer Protocol Secure). Alongside SFTP, FTPS provides encrypted data transfers, ensuring that the data is secure in transit. Crucial not only for your own server but also when using third-party providers.

2. Use the Most Secure Encryption

Use robust encryption tools. The most advanced standard is AES-256 provides advanced encryption against a wide range of cyber threats. AES is highly efficient, with strong encryption capabilities making it ideal for SFTP.

Operates by encrypting data in fixed blocks, typically of 128 bits. However, 192 or 256-bit keys also work for enhanced security. This level of encryption ensures that data transferred via SFTP is secure from interception and unauthorized access. By implementing AES encryption, you encrypt all data, including files, login credentials, and commands during transfer. 

3. Use Hashing Algorithms

Hashing algorithms help determine data integrity during transfers. Ideally, a hash is a unique alphanumeric value created when you pass data through an hashing algorithm. Therefore, it’s crucial to ensure that your SFTP server uses the right hashing algorithm. The algorithm ensures that the data sent matches the data received and it has not been compromised while in transit.

To safeguard your data, it’s crucial you use robust hashing algorithms like SHA-2. SHA-2 is a family of algorithms such as SHA-225, SHA-238, SHA-256 and SHA-512, which are less susceptible to cyber attacks. These algorithms provide a higher level of security compared to older hashing methods such as SHA-1. If you are using the older version, it’s crucial to migrate to SHA-2.

4. Use File and Folder/Directory Security

To maintain the security of files in your SFTP, it’s important to implement proper access controls. This includes setting permissions to restrict access to sensitive data. By setting such controls, only authorized users gain access, view files, and make modifications. Also, it’s imperative to provide users with access to data that they need, and restrict access to data they don’t need.

To implement file and folder security in SFTP, use the Chroot Jail mechanism. This method restricts SFTP users to specific directories, minimizing the risk of unauthorized access and data breaches. Start by creating an SFTP group to manage user access and then establish a new user without a home directory. Configure the user’s home directory to the desired location and ensure that the folder has the correct ownership and permissions.

To further enhance security, disable SSH shell access for the user and add the user to the SFTP restricted group. Implement key-based authentication for enhanced security and adjust the SSHD configuration file to specify the key’s location and use ‘internal-sftp’ as the SFTP subsystem. Lastly, configure the Chroot Jail by specifying the desired directory and enforcing the use of ‘internal-sftp.’

5. Secure Your SFTP Behind a Firewall

A firewall helps secure your SFTP server and prevents insecure connections. The firewall filters both ongoing and outgoing traffic, and blocks malicious access. 

Make sure you update your firewall regularly. Also, often monitor logs to detect suspicious activities. Further enhance it by performing regular penetration tests. It ensures you detect vulnerabilities much earlier and perform the required patches. Besides, limit the SFTP from internet access unless it’s necessary for operations. If not required, configure the firewall to block all external access to the SFTP server.

6. Use IP Deny and Allow Lists

IP Allow and Deny lists help limit access to your SFTP server. They enable you to specify which IP addresses are authorized to connect and control who accesses your sensitive files and blocks unauthorized access. 

Configuring your SFTP server to block malicious or suspicious IP addresses significantly reduces the risk of cyber threats such as DoS. On the other hand, allow lists ensure that only trusted IPs can access the server, adding an extra layer of security. This comes in handy especially when using the SFTP in a controlled environment or when you have the correct IPs of all users.

7. Use Strong Passwords

Strong passwords help deter hackers from accessing your SFTP server/clients easily. They act as the first line of defense, especially when using SaaS tools. 

Besides a strong passwords also choose a robust password manager to avoid storing passwords in your browser.

Moreover, it’s crucial to create a password policy. It dictates the nature of passwords, how regularly you should change them, and more. 

8. Avoid Exposing SSH Keys

SSH keys are basically the gateway to your server. With the SSH keys and server IP address, it is easy to gain access. So, please store your keys in such a way that no one can access them. 

Regularly rotate SSH keys and store them in a secure location, such as a hardware security module (HSM) to prevent unauthorized access. It’s also crucial to audit the use of SSH keys to ensure they are not being misused.

9. Monitor Server Logs

Server logs store crucial information about all activities in the server. They help track user activity and detect any suspicious activities such as unauthorized file access and transfers. Hence, please regularly review your server logs and implement a real time alerting system to notify you of any suspicious behaviour. I

10. Educate Users About SFTP Security

User awareness is crucial when it comes to securing your SFTP file transfers. It’s important to inform all users about the best SFTP server security practices. This creates a security first culture within the organization, which contributes to overall data protection.

SFTP Security: How to Secure File Transfers with SFTP Conclusion

The above 10 measures are some of the best ways to secure file transfers in SFTP. Ideally, securing file transfers requires taking an all round approach to secure the entire SFTP environment. By implementing the above measures and continuously updating security practices, you significantly improve the security of their SFTP and stay compliant with data regulatory standards

Avatar for Dennis Muvaa
Dennis Muvaa

Dennis is an expert content writer and SEO strategist in cloud technologies such as AWS, Azure, and GCP. He's also experienced in cybersecurity, big data, and AI.

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