How to Create SSH Port Forwarding

Secure Shell (SSH) is a widely-used protocol for securely accessing remote systems over an unsecured network. One of the fundamental aspects of SSH is understanding what port is SSH typically configured to use. By default, SSH operates on port 22, but this can be changed for security reasons. This blog post will delve into the intricacies of SSH, its default port, how to change it, and best practices for securing your SSH connections.

Table of Contents

Understanding SSH and Its Default Port

SSH, or Secure Shell, is a cryptographic network protocol designed to provide secure communication over an unsecured network. It is commonly used for remote login, command execution, and file transfers. The default port for SSH is 22, which means that when you attempt to connect to a remote server using SSH, the connection is typically established on this port.

However, it's important to note that while port 22 is the default, it is not the only port that SSH can use. Administrators often change the default port to enhance security by making it more difficult for automated attacks to target their systems. Changing the port can be a simple yet effective measure to reduce the risk of unauthorized access.

Why Change the Default SSH Port?

Changing the default SSH port from 22 to another port can provide several security benefits:

Reduced Exposure to Automated Attacks: Many automated attacks, such as brute-force attacks, target the default SSH port 22. By changing the port, you can significantly reduce the likelihood of these attacks.
Enhanced Security Through Obscurity: While not a foolproof method, changing the port adds an extra layer of security by making it less obvious to potential attackers where to find your SSH service.
Compliance with Security Policies: Some organizations have security policies that require changing default ports to comply with internal or external security standards.

How to Change the Default SSH Port

Changing the default SSH port is a straightforward process that involves modifying the SSH configuration file. Here are the steps to change the default SSH port on a Linux system:

Open the SSH Configuration File: Use a text editor to open the SSH configuration file, typically located at /etc/ssh/sshd_config.
Edit the Port Setting: Look for the line that specifies the port. It will look something like this:
```
    #Port 22
    
```
Uncomment this line by removing the # at the beginning and change the port number to your desired port. For example, to change it to port 2222, you would edit the line to:
```
    Port 2222
    
```
Save and Close the File: Save the changes and close the text editor.
Restart the SSH Service: Restart the SSH service to apply the changes. You can do this with the following command:
```
    sudo systemctl restart sshd
    
```

🔒 Note: After changing the port, make sure to update your firewall rules to allow traffic on the new port. For example, if you are using UFW (Uncomplicated Firewall), you can allow the new port with the following command:

sudo ufw allow 2222/tcp

Best Practices for Securing SSH

Changing the default SSH port is just one of many steps you can take to secure your SSH connections. Here are some additional best practices:

Use Strong Passwords: Ensure that all user accounts have strong, unique passwords. Consider implementing a password policy that enforces complexity and regular changes.
Enable Key-Based Authentication: Instead of relying on passwords, use SSH keys for authentication. This method is more secure and less susceptible to brute-force attacks.
Disable Root Login: Prevent direct root login by setting PermitRootLogin no in the SSH configuration file. This forces attackers to use a regular user account, which can be more easily monitored and restricted.
Limit SSH Access: Restrict SSH access to specific IP addresses or ranges using the AllowUsers or AllowGroups directives in the SSH configuration file. This can be combined with firewall rules to further limit access.
Regularly Update SSH Software: Keep your SSH software up to date to protect against known vulnerabilities. Regular updates ensure that you have the latest security patches and features.

Common SSH Ports and Their Uses

While port 22 is the default for SSH, there are other ports that are commonly used for various purposes. Here is a table of some common SSH-related ports and their uses:

Port Number	Protocol/Service	Description
22	SSH	The default port for SSH connections.
2222	SSH	A common alternative port for SSH to avoid default port attacks.
2022	SSH	Another alternative port for SSH, often used in environments where port 2222 is already in use.
2200	SSH	Yet another alternative port for SSH, providing additional flexibility.
10022	SSH	A higher port number that can be used to avoid conflicts with other services.

Troubleshooting SSH Port Changes

If you encounter issues after changing the SSH port, here are some common troubleshooting steps:

Check Configuration File: Ensure that the SSH configuration file has been edited correctly and that there are no syntax errors.
Verify Service Status: Check the status of the SSH service to ensure it is running. Use the command:
```
    sudo systemctl status sshd
    
```
Review Firewall Rules: Make sure that your firewall rules allow traffic on the new port. Use the appropriate commands to check and modify your firewall settings.
Test Connectivity: Use tools like telnet or nc (netcat) to test connectivity to the new port. For example:
```
    telnet your_server_ip 2222
    
```

By following these troubleshooting steps, you can identify and resolve most issues related to changing the SSH port.

Changing the default SSH port is a simple yet effective way to enhance the security of your SSH connections. By understanding what port is SSH configured to use and implementing best practices, you can significantly reduce the risk of unauthorized access and protect your systems from potential threats. Regularly reviewing and updating your SSH configuration ensures that your systems remain secure and compliant with best practices.

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