How to Securely Change the SSH Port on CentOS 7

Securing your SSH service is crucial in maintaining the integrity and safety of your system. One key aspect of this is changing the default SSH port from the often targeted 22 to a less commonly used port like 2222. In this guide, we’ll walk you through the process step-by-step on how to change the SSH port on CentOS 7. We’ll also discuss why security by obscurity is not typically recommended and the potential risks involved.

Step-by-Step Guide to Changing the SSH Port on CentOS 7

In order to change the SSH port on CentOS 7, follow these essential steps:

Edit the SSH Server Configuration: The SSH server configuration file is located at /etc/ssh/sshd_config. You’ll need to modify this file to specify the new port. Open the file with a text editor: Open the sshd_config file and change the port: Port 2222
AddressFamily any
ListenAddress 0.0.0.0
ListenAddress :: Open the New Port in Firewall: To allow traffic through this new port, it needs to be configured in the firewall: Use the firewall-cmd command to add the new port to the firewall: firewall-cmd --permanent --zonepublic --add-port2222/tcp Reload the firewall rules to apply the changes: firewall-cmd --reload Tell SELinux to Use the New Port: If SELinux is enabled, you need to tell it that the new port should be used for SSH. This can be done with the semanage command. First, ensure the policycoreutils-python package is installed: Install the necessary package if it is not already installed: yum install -y policycoreutils-python Now, add the new port to the SELinux context: semanage port -a -t ssh_port_t -p tcp 2222 Restart SSH Service: After making all the necessary changes, restart the SSH service to ensure everything is working correctly: systemctl restart sshd Test the New Configuration: Finally, disconnect from the remote host and try to log in again using the new port: ssh -p 2222

It is important to follow these steps to ensure that your SSH service is properly configured on CentOS 7.

Considerations and Risks

Before making any changes to your SSH port configuration, it's important to understand the context and implications:

Security by Obscurity: Security by obscurity means hiding the information about system vulnerabilities to prevent attackers from exploiting them. While changing the default SSH port can add an additional layer of security, it is generally not considered a strong security practice. Testing Time vs. Time to Detect: Changing the SSH port to a less commonly used port will likely take you longer to configure than it would take an attacker to use a port scanner to detect it. This means that security by obscurity may not be effective. Corporate Environment Restrictions: In a corporate environment, other services and protocols may require connections to specific ports. Changing the SSH port may negatively impact productivity or functionality. Demonstrating Knowledge: In a test scenario, you may be asked to change the SSH port to demonstrate your knowledge of network security. However, it is more valuable to emphasize why changing the port is not ideal and the potential risks involved. Best Practices: Maintain proper security practices by regularly updating your SSH server, using strong passwords, and configuring protection against potential attacks.

While changing the SSH port can add a layer of security, it is important to consider the potential risks and understand why it may not be the best solution in certain contexts. Always prioritize structured security practices such as regular updates and strong password policies.