In today’s online world, ensuring secure communication has become a topmost concern for all establishments since significant operations are executed by transmitting data from one device to another via the network.
As a result, multiple approaches are being adopted to guarantee complete protection and maintain the authenticity of the data during transmission. Certain corporations handle sensitive information that requires safeguarding. Hence, they establish regulations for communicating with external devices via the Internet.
The Secure Shell Protocol or SSH is a technique and protocol established to link a client and server securely. It facilitates data transfer from the client to the server as a protocol.
Before transmission, the system encrypts all data and decrypts it at the receiving end. A port is mandatory to initiate all communications between two devices (either wired or wireless) over a network via SSH.
This article will enlighten you on the SSH port and provide you with all the necessary information.
What is SSH?
SSH is a protocol used to remotely access servers. It provides a secure way to connect to a device over an unsecured network. It encompasses not only security services but also a set of utilities that facilitate the implementation of the SSH protocol.
SSH evolved from the conventional telnet protocol. Nevertheless, telnet lacked security features and was consequently substituted by SSH gradually. In case you are a system manager, you may have employed SSH.
SSH has numerous features, including:
- It offers robust password authentication, encrypted data communication, and public-key authentication.
- It enables remote management of systems and applications, allowing others to use a different computer and perform various tasks.
- It is a cryptographic network protocol that follows the client/server model.
- It also allows you to create secure tunnels for various application protocols. These protocols are used for terminal emulation or file transfer.
What is SSH used for?
SSH is an essential component of all data centers and comes pre-installed on every Unix, Linux, and Mac server.
It is widely used to safeguard various communication forms between a local device and a remote host, such as secure remote access to resources, command execution, software patch delivery, and administrative or management duties.
Aside from establishing a secure link between local and remote machines, SSH is employed to administer routers, server hardware, virtualization platforms, operating systems, and internal systems management and file transfer software.
The Secure Shell protocol is utilized to connect to servers, effect modifications, conduct uploads and exit, either utilizing software or directly through the terminal.
SSH keys are implementable to automate server entry and are often employed in scripts, backup systems, and configuration management tools. SSH keys are designed to be user-friendly and work seamlessly across organizational boundaries, offering single sign-on (SSO) so that users can switch between their accounts without needing to enter a password every time.
Apart from authenticating over an encrypted connection, SSH plays a crucial role in identity and access management. All SSH traffic is encrypted, ensuring that users' activities remain confidential, whether transferring a file, browsing the web or executing a command.
Although employing an average user ID and password as credentials is feasible, SSH mostly depends on public key pairs to verify hosts to one another. Nonetheless, users must still utilize their user ID and password, or other authentication techniques, to establish a connection to the remote host.
However, the local and remote machines authenticate individually to each other. This is achieved by creating an exclusive public key pair for each host engaged in communication. Two public key pairs are needed for a single session: one to verify the remote machine to the local machine and another to authenticate the local machine to the remote machine.
What is an SSH port?
For every SSH communication, a port must establish and initiate the communication. An SSH port is a prerequisite regardless of the device's connectivity mode.
There are over 65k ports available for communication, and any of these can be employed to initiate communication. The default port number is used for all communications but can be altered and assigned to any other open port number.
When a user executes the Linux command for network-based communication between two devices, the connection automatically uses the default SSH port number 22. However, if you are engaged in any important communication that demands high security, it is advisable to alter the default SSH port number to a different one to prevent a brute-force attack.
It is common knowledge that 22 is the default SSH port number and is highly susceptible to attacks, rendering your transmitted information vulnerable to hacking.
What is the default port number for SSH?
The standard port number for SSH is 22, but it is not recommended for sensitive data transfers due to security concerns. It is advisable to use a different port number to prevent brute-force attacks. In total, there are 65,536 communication ports available.
This port serves as the starting point for every connection, and in some cases, changing the default SSH port number is essential to enhance security measures against brute force attacks and safeguard the server.
When discussing brute force assault, it is an inaccurate technique to penetrate incorrect data—for example, determining passwords through exhaustive trials instead of algorithms. This implies attempting various possibilities until the code is decoded.
Furthermore, since Port 22 is the default communication port, it makes it easier for unauthorized individuals to access data. If you alter this port to another, the intruder must test multiple other ports to find an open one. Consequently, this move may be taken to keep any hacker at bay.
How does SSH port work?
After understanding the notion of an SSH port, let's delve into how the SSH port operates. After procuring a Linux VPS, users typically resort to Telnet, rlogin (remote login), or rsh (remote shell), which are vulnerable emulation or login applications.
SSH can offer identical features and functionalities as an alternative to these three. Additionally, to substitute the file transfer program SSH can replace RCP (remote copy) and FTP (File Transfer Protocol).
When employing the SSH protocol, two devices are involved - one acts as the server while the other serves as the client. The SSH client initiates the connection, and public-key cryptography is utilized to authenticate the SSH server.
Once the connection is established, the SSH protocol deploys strong symmetric encryption and hashing techniques to ensure the confidentiality and integrity of the data transmitted between the client and server.
To establish a terminal session with a remote host, SSH can be utilized by executing the following command:
This command enables the client to connect with the server (server.example.com) through the user ID (UserName).
Although a conventional user ID and password can be utilized for accessing SSH, public key pairs are more commonly employed for authenticating hosts to one another.
Usually, while working with the SSH protocol, the following three steps are taken into account:
- Establishing an SSH connection
- Negotiating session encryption
- Authenticating the user
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How to change the default SSH Port?
To modify the default SSH port, you need to modify the sshd_config file. Additionally, it's always advisable to keep a backup of your file.
Use the following command to create a backup initially:
ubuntu@ubuntu:~$ cp /etc/ssh/sshd_config /etc/ssh/sshd_config_backup
This command generates a duplicate of the file in the same directory.
Next, proceed to change the default SSH port. Open the ssh_config file in any text editor. Then, insert the following command:
ubuntu@ubuntu:~$ gedit /etc/ssh/sshd_config
Once you execute this command, the specified file will open in the text editor. Look for this line in the code:
#Port 22
Assuming you want to modify your port number to 45673, you can remove the hash (#) sign and substitute 22 with your desired port number.
Here's an example:
Port 45673
Furthermore, add this port to your firewall's whitelist to prevent being locked out of your device. Now, let's proceed to restart SSH. To apply the modifications and restart the server, enter the following command:
ubuntu@ubuntu:~$ sudo service sshd restart
Once your device restarts, you should be able to see the changes you made. It's important to note that one of the most critical security measures is modifying the default SSH port number as soon as you purchase a Linux VPS.
You can easily test the changes without logging out of your SSH session.
What is SSH port forwarding?
SSH port forwarding, also referred to as SSH tunneling, is a method that allows a user to establish a secure connection between a local host and a remote host.
By redirecting network traffic to a specific port/IP address, SSH port forwarding enables applications on the local host to access a remote host directly. The target location may be on the remote SSH server, or the server may be configured to forward to another remote host.
This function can be used to evade firewalls, secure outdated software, and is commonly used by IT professionals and system administrators to enter the internal network from their personal devices.
However, it is important to note that hackers and viruses can exploit this feature to access the internal network via the Internet.
Conclusion
The secure shell network is the widely used approach for safeguarding device connections on networks. Numerous corporations have incorporated SSH protocols to guarantee the full security of data transfers.
Although the default SSH port number is 22, it can pose a risk in certain situations involving critical information transfer. It is advisable to alter the SSH port number to prevent brute-force attacks.
This article provides a comprehensive overview of the features and functions of SSH Port Numbers. It also outlines the steps to modify the default SSH port number per your needs.
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