As an expert guide to server security, it’s important to understand the risks involved with using default settings. One such setting is the default port number used by the SSH server. By default, the SSH server uses a well-known port number that can be targeted by attackers. Changing the port number can improve the security of your server and reduce the risks of potential threats. In this article, we’ll provide a step-by-step guide on how to change the SSH server port number and provide some best practices for securing your server.
Understanding the SSH Server Port
The SSH server port is a crucial element of allowing remote access to your server through a TCP/IP network. This allows you to access the server remotely via a terminal or console from anywhere in the world. The default port number for SSH is 22, which is well-known and commonly used by attackers to attempt unauthorized remote access.
The SSH server port is part of the transport layer of the TCP/IP model and is responsible for establishing and managing connections between devices. Without this port, remote access to the server is impossible. It is essential to understand the function of the SSH server port to appreciate why changing the default port number is necessary.
Why Change the SSH Server Port Number?
The default SSH server port number is well-known, and as a result, it is a prime target for attackers looking to gain unauthorized remote access. By changing the default port number, you can reduce the risk of potential security threats. Additionally, changing the port number can limit unauthorized remote access attempts, improving the overall security of your server.
When you use the default SSH port number, your server is more vulnerable to attacks that target that port. Hackers can use a variety of techniques to gain unauthorized access, such as brute-force attacks and port scans. With a well-known port number, these attacks can be easier to execute. By changing the port number, you can make it more difficult for attackers to gain access to your server.
Changing the SSH server port number is easy to do, and it can make a big difference in the security of your server. By reducing the risk of unauthorized access attempts, you can ensure that your server is only accessible by those who are authorized and that your data is safe and secure.
Preparing to Change the SSH Server Port Number
Before changing the SSH server port number, it is important to prepare for the process by backing up the current configuration file and verifying the current port number.
Backing up the Configuration File
The configuration file contains important system settings and is responsible for managing the SSH server port number. It is essential to back up the configuration file before making any changes to ensure that the system can be restored to its previous state if necessary.
To back up the configuration file, simply copy it to a separate location on your server or to an external device for safekeeping.
Verifying the Current Port Number
Before changing the SSH server port number, it is important to verify the current port number to ensure that you have the correct information. To do this, open the configuration file and search for the “Port” directive.
The Port directive specifies the port number used by the SSH server. The default port number is 22, but it may have been changed by the administrator. If you find that the port number is already different from the default, note the current value for future reference.
It is essential to ensure that no other services are using the port number you plan to change to. To do this, use the command “netstat -tuln | grep PORT_NUMBER” to check if any services are already using the port number you plan to change to.
Changing the SSH Server Port Number
In order to change the SSH server port number, you will need to access the configuration file of your SSH server. This guide will walk you through the necessary steps to make this change.
Before making any changes, it is important to backup your configuration file to ensure that you can revert back to the previous settings if needed.
| Step | Description |
|---|---|
| 1 | Open the configuration file with your preferred text editor. The location of the file may vary depending on your operating system and SSH server software. |
| 2 | Locate the line that specifies the default port number, which is usually 22. |
| 3 | Change the default port number to a new, unused port number between 1024 and 65535. Make sure that the port number you choose is not already in use by another program, as this will cause conflicts. |
| 4 | Save and close the configuration file. |
Once you have made these changes, you will need to restart your SSH server for them to take effect. This can usually be done using the following command:
sudo systemctl restart ssh
After restarting the SSH server, verify that the new port number is being used by attempting to connect to your server using the new port number. If successful, you should be able to access your server as usual.
If you encounter any issues, you can revert back to the previous settings by restoring the backup of your configuration file.
Additional Considerations
Keep in mind that changing the SSH server port number is just one step in securing your server. It is also important to consider other security measures, such as implementing password policies, limiting access, and auditing logs for suspicious activity.
By taking these steps, you can improve the overall security of your SSH server and reduce the risks of potential threats.
Changing the SSH Server Port Number
After you have backed up the configuration file and verified the current port number, you can proceed with changing the SSH server port number. This can be done using the command-line interface of the server and changing the port number in the configuration file. Here are the steps:
- Log in to the server as the root user or a user with sudo privileges.
- Open the SSH configuration file using a text editor. The location of the file may vary depending on your server’s operating system and SSH version. However, it is commonly found at /etc/ssh/sshd_config. For example, you can use the following command to open the file using the nano text editor:
sudo nano /etc/ssh/sshd_config
- Find the line that specifies the SSH server port number. It should look like this:
| Original Configuration | Explanation |
|---|---|
Port 22 | The default SSH server port number. |
- Change the port number to a value between 1024 and 65535. Make sure it is not in use by another application or service. For example:
| New Configuration | Explanation |
|---|---|
Port 2222 | The new SSH server port number. |
- Save the changes to the configuration file and exit the text editor.
- Restart the SSH service to apply the changes. The command may vary depending on your server’s operating system and SSH version. For example, you can use the following command:
sudo service ssh restart
After completing these steps, the SSH server should be running on the new port number. Verify this by testing the server’s remote access with the new port number.
Verifying the New SSH Server Port Number
It is important to verify the new SSH server port number to make sure the changes were successful. This can be done by testing the server’s remote access with the new port number. Here are the steps:
- Open a new terminal window or command prompt on your local computer.
- Connect to the SSH server using the new port number. The command may vary depending on your local operating system and SSH client. For example, you can use the following command:
ssh username@serverip -p 2222
- Enter the password for the user account on the SSH server.
- If you are able to connect to the server, the new SSH server port number is working properly.
Reverting the Changes
If for any reason you need to revert the changes made to the SSH server port number, it can be done easily by restoring the backup of the configuration file. Here are the steps to follow:
- Access the backup of the configuration file that you created before making changes to the SSH server port number.
- Copy the backup of the configuration file to the SSH server’s directory where the original configuration file is saved.
- Rename the backup of the configuration file to the original name of the configuration file.
- Restart the SSH service to apply the changes.
Once these steps are completed, your SSH server should be reverted back to its original state with the default port number.
It is important to make sure that you have access to the backup file before making any changes to the SSH configuration file. This ensures that you can quickly and easily revert any changes if necessary.
Best Practices for Securing Your SSH Server
When it comes to securing your SSH server, it’s essential to follow best practices to minimize the risk of unauthorized access or other security threats. Here are some guidelines that can help you protect your server:
Use Strong Passwords
Using strong passwords is crucial in preventing unauthorized access to your server. Make sure to use a combination of uppercase and lowercase letters, numbers, and special characters in your passwords. Additionally, it’s a good practice to change passwords at regular intervals and avoid using the same password for multiple accounts.
Limit Access to Your SSH Server
It’s important to limit access to your SSH server to only authorized users. This can be done by disabling root login and creating separate user accounts with limited permissions. You can also use firewall rules to restrict access to specific IP addresses or ranges.
Audit Logs for Suspicious Activity
Monitoring your server logs is a crucial part of SSH server security. Regularly reviewing logs can help you identify and respond to suspicious activity, such as login attempts and file modifications. You can use tools like logwatch and fail2ban to automate log monitoring and protect against brute-force attacks.
Enforce Two-Factor Authentication
Two-factor authentication adds an additional layer of security to your SSH server by requiring users to provide a second form of authentication in addition to a password. This can be done using tools like Google Authenticator or YubiKey. Using two-factor authentication can provide greater security, especially for sensitive accounts and data.
Regularly Update Your Software
Keeping your software up-to-date is essential for maintaining the security of your SSH server. Regularly applying security patches and updates can help you protect against known vulnerabilities and reduce the risk of attacks that exploit them. It’s also recommended to use long-term support (LTS) versions of software, as they receive security updates for a longer period of time.
Conclusion
By following these best practices, you can significantly improve the security of your SSH server and reduce the risk of security threats. While these guidelines are a good starting point, it’s important to stay up-to-date with the latest security trends and adapt your practices accordingly to ensure your server remains secure.
FAQ
Q: Can changing the default SSH port number really improve security?
A: Yes, changing the default SSH port number can improve security by reducing the risk of potential threats. Attackers often target well-known default port numbers, so changing it can help minimize unauthorized remote access attempts.
Q: What happens if I forget my new SSH server port number?
A: If you forget the new SSH server port number, you may not be able to connect to your server. It’s important to keep a record of the new port number and store it in a secure location.
Q: Do I need to restart the SSH service after changing the port number?
A: Yes, after changing the SSH server port number, you need to restart the SSH service for the changes to take effect. You can do this by using the command “sudo service ssh restart”.
Q: Can I change the SSH server port number to any value?
A: Yes, you can change the SSH server port number to any non-reserved port number. However, it’s important to ensure that the new port number is not already in use by another service.
Q: Can changing the SSH server port number cause any issues with my server?
A: No, changing the SSH server port number should not cause any issues with your server. However, it’s important to ensure that the new port number is not blocked by any firewalls or security policies.
Q: What are some common best practices for securing an SSH server?
A: Some common best practices for securing an SSH server include using strong passwords, limiting access to only authorized users, disabling root login, regularly auditing logs for suspicious activity, and keeping the SSH server software up to date.
