Install SSH Server on Ubuntu: A Quick and Secure Guide

Setting up an SSH server on Ubuntu is a straightforward process, essential for remote access and server management. This guide will walk you through the basic installation and highlight crucial security measures to protect your server.

To begin, update your package lists to ensure you have the latest versions:

sudo apt update

Next, install the OpenSSH server package:

sudo apt install ssh

Once installed, the SSH service should start automatically. You can verify its status with:

sudo systemctl status ssh

For basic connectivity, especially if you have a firewall enabled like ufw, you need to allow SSH traffic on port 22:

sudo ufw allow 22

While these steps provide a functional SSH server, it’s crucial to understand that the default configuration is not secure enough for a public-facing server. Leaving it as is exposes you to significant security risks.

Security Hardening is Essential

The default SSH setup allows unlimited password attempts on the standard port, and while direct root login is disabled, vulnerabilities remain. If your username and password are easily guessable and your server is accessible from the internet, unauthorized access is a real possibility.

To significantly enhance your SSH server’s security, consider these essential hardening steps:

• Key-Based Authentication: The most crucial security improvement is to switch to SSH keys and disable password-based logins altogether. Key-based authentication is far more secure than passwords, making brute-force attacks virtually impossible.
• Change the Default SSH Port: Moving SSH to a non-standard port (ideally in the range of 20000-60000) drastically reduces automated attacks. Bots constantly scan for SSH on port 22; changing the port makes your server significantly less visible.
• Implement fail2ban: fail2ban is a powerful intrusion prevention software that monitors log files for malicious activity, like excessive failed login attempts, and automatically blocks offending IP addresses. This is essential for mitigating brute-force attacks.

Implementing these security measures will take minimal time but dramatically increase your server’s security, reducing the risk of unauthorized access from a significant probability to an almost negligible one. This assumes you practice good key management, use a strong passphrase for your SSH key, and avoid publicly sharing your credentials.

Accessing Your SSH Server from the Internet

If you intend to access your SSH server from outside your local network, you might encounter network address translation (NAT) issues, especially if your server is behind a home router. In such cases, you’ll need to configure port forwarding on your router to direct incoming SSH traffic on your chosen port to your Ubuntu server’s internal IP address. If external access is not required, skipping port forwarding greatly enhances your network security.

By following these steps and prioritizing security hardening, you can confidently install and use an SSH server on Ubuntu for secure remote access and server management.