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5 Best OpenSSH Server Best Security Practices

OpenSSH is a widely used protocol for secure remote access to servers. However, like any software, it requires proper security measures to protect against unauthorized access and potential threats. In this blog post, we will explore the 5 best security practices for OpenSSH servers to ensure their integrity and confidentiality.

2026-03

Table of Contents#

  1. Keep OpenSSH Up-to-Date
  2. Use Strong Authentication Methods
  3. Limit Access to the SSH Server
  4. Disable Unnecessary Features
  5. Monitor and Log SSH Activity

1. Keep OpenSSH Up-to-Date#

One of the most important security practices for any software is to keep it up-to-date. OpenSSH developers regularly release security patches and bug fixes to address known vulnerabilities. By keeping your OpenSSH server up-to-date, you ensure that it has the latest security enhancements and protection against emerging threats.

How to Update OpenSSH#

The process of updating OpenSSH depends on your operating system. Here are some general steps:

  • Debian/Ubuntu: 
    sudo apt update
sudo apt upgrade openssh-server
  • CentOS/RHEL: 
    sudo yum update openssh-server
  • Arch Linux: 
    sudo pacman -Syu openssh

2. Use Strong Authentication Methods#

Password-based authentication is the most common method for accessing an SSH server. However, passwords can be easily guessed or brute-forced if they are weak. To enhance the security of your SSH server, it is recommended to use strong authentication methods such as public-key authentication.

Public-Key Authentication#

Public-key authentication is a more secure method of authentication that uses a pair of cryptographic keys (public and private) instead of a password. Here are the steps to set up public-key authentication:

  1. Generate a Key Pair:
    • On your local machine, generate a key pair using the ssh-keygen command. For example:
    ssh-keygen -t rsa -b 4096
    • Follow the prompts to specify the location and passphrase for the key pair.
  2. Copy the Public Key to the Server:
    • Use the ssh-copy-id command to copy your public key to the server. For example:
    ssh-copy-id user@server
    • Replace user with your username on the server and server with the server's IP address or hostname.
  3. Configure the Server:
    • On the server, edit the /etc/ssh/sshd_config file and ensure that the following options are set:
    PubkeyAuthentication yes
AuthorizedKeysFile.ssh/authorized_keys
    • Save the file and restart the SSH server.

3. Limit Access to the SSH Server#

By default, an SSH server listens on port 22 and allows connections from any IP address. To enhance the security of your SSH server, it is recommended to limit access to only trusted IP addresses or networks.

How to Limit Access#

  1. Change the SSH Port:
    • Edit the /etc/ssh/sshd_config file and change the Port option to a non-standard port (e.g., 2222). For example:
    Port 2222
    • Save the file and restart the SSH server.
  2. Use Firewall Rules:
    • Use a firewall to restrict access to the SSH port. For example, on a Linux system with iptables, you can use the following commands:
    sudo iptables -A INPUT -p tcp --dport 2222 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 2222 -j DROP
    • Replace 2222 with the port number you specified in step 1.

4. Disable Unnecessary Features#

OpenSSH comes with several features that may not be required for your specific use case. Disabling unnecessary features can reduce the attack surface of your SSH server and enhance its security.

How to Disable Features#

  1. Disable Password Authentication:
    • Edit the /etc/ssh/sshd_config file and set the following option:
    PasswordAuthentication no
    • Save the file and restart the SSH server.
  2. Disable X11 Forwarding:
    • If you don't need to forward X11 applications over SSH, edit the /etc/ssh/sshd_config file and set the following option:
    X11Forwarding no
    • Save the file and restart the SSH server.
  3. Disable Agent Forwarding:
    • If you don't need to forward SSH agent connections over SSH, edit the /etc/ssh/sshd_config file and set the following option:
    AllowAgentForwarding no
    • Save the file and restart the SSH server.

5. Monitor and Log SSH Activity#

Monitoring and logging SSH activity can help you detect and respond to potential security incidents. By reviewing the SSH logs regularly, you can identify unauthorized access attempts, suspicious activity, and other security issues.

How to Monitor and Log SSH Activity#

  1. Enable Logging:
    • Edit the /etc/ssh/sshd_config file and ensure that the following option is set:
    SyslogFacility AUTHPRIV
LogLevel INFO
    • Save the file and restart the SSH server.
  2. Review the Logs:
    • Use the tail command to view the SSH logs. For example:
    tail -f /var/log/auth.log
    • Replace /var/log/auth.log with the path to the SSH log file on your system.

Conclusion#

By implementing these 5 best security practices for OpenSSH servers, you can enhance the security of your remote access and protect your server against unauthorized access and potential threats. Remember to keep your OpenSSH server up-to-date, use strong authentication methods, limit access, disable unnecessary features, and monitor and log SSH activity.

References#