Secure Shell (SSH) is a protocol primarily used for secure connections between computers. Often, it is critical in managing systems remotely, ensuring secure file transfers, and executing commands across networks. By default, SSH uses port 22, making it a common target for brute force attacks and unauthorized access attempts. Changing the SSH port can be an effective measure to enhance security by reducing the risk of automated attacks. This article provides a fundamental understanding of SSH ports and a detailed guide on how to change the SSH port to bolster your system’s security.
Understanding the Basics of SSH Ports
SSH operates on a client-server model, where the client connects to a server to establish a secure communication channel. By default, SSH communicates over port 22, which is the designated port for this protocol. This port is where the server listens for incoming SSH connections. The ubiquity of port 22 makes it a predictable target for potential attackers. Port scanning scripts often check this port to find exploitable connections, thereby making it a focal point for security breaches.
Changing the default SSH port is a basic but effective layer of security. Moving away from port 22 to a less predictable port number reduces the visibility of SSH services to automated attacks, which primarily target default settings. It’s a simple measure that can significantly decrease the likelihood of being targeted by random scans and automated login attempts. However, it is important to recognize that changing the SSH port is not a solution for all security concerns but rather a preliminary step that should be part of a broader security strategy.
When selecting a new port, it is essential to choose a number that does not conflict with other standard or well-known ports used by other essential services. The port number should be between 1024 and 65535, as these are designated as "registered" ports and "dynamic" or "private" ports, which are generally not assigned by Internet Assigned Numbers Authority (IANA) for specific services. This range helps avoid port conflicts and potential service disruptions.
Step-by-Step Guide to Changing Your SSH Port
To change the SSH port on your server, you must have administrative rights or access to modify the SSH daemon configuration files. Start by logging into your server with sufficient privileges. You can access your server through SSH itself if you are working remotely or through a local terminal if you have direct access. Make sure to backup your current SSH configuration before making changes to avoid any unintended service interruptions.
Next, open the SSH configuration file in your preferred text editor. This file is typically found at /etc/ssh/sshd_config. Use a command line text editor such as nano or vi. For instance, you could enter sudo nano /etc/ssh/sshd_config in your terminal. Once you have the file open, look for the line that reads #Port 22. The ‘#’ symbol indicates that this line is commented out. Change the line by removing the ‘#’ to uncomment it and change ’22’ to your new chosen port number, for example, Port 2222. Ensure that no other service is using the port you select by checking the /etc/services file for any potential conflicts.
After modifying the port number, save the changes and exit the text editor. For the changes to take effect, restart the SSH service. This can be done by running the command sudo systemctl restart sshd on systems using systemd, or sudo service ssh restart on systems using init. Once restarted, verify that SSH is operating on the new port by attempting to connect using the new port number, e.g., ssh -p 2222 username@yourserver.com. Be sure also to update any firewall rules to allow traffic on the new SSH port to ensure continuous connectivity.
Changing the default SSH port is a straightforward yet effective security measure that can help shield your servers from some common types of cyber attacks. While it does not provide complete protection against dedicated intruders, it significantly lowers your profile on the internet landscape, making your system less conspicuous to opportunistic scans. Always remember, this should be just one aspect of a comprehensive security plan, which should include robust authentication methods, regular updates, and continuous monitoring for any suspicious activity. Taking these steps will significantly fortify your network’s defenses against potential threats.
