What is SSH? – Definition, How does it work, SSH Ports and More

What is SSH?

The SSH, Secure Shell, is a remote management protocol through which users can both modify and control their remote servers on the Internet.

It was created to replace Telnet, an unencrypted protocol and therefore did not offer any security to users.

Instead, SSH makes use of the most innovative cryptography techniques with the clear objective that all communications made between users and remote servers are secure. It has a tool that allows the remote user to authenticate to exit later back to the users.

It is worth noting that users of the Linux and macOS operating systems can implement the SSH protocol on their remote servers very easily through the terminal. Of course, Windows users can also do it, although the procedure is different.

SSH encryption

In the field of computer security, three concepts are interesting to know:

• Symmetric encryption
• Asymmetric encryption
• Hashing.

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How does it work?

In both Linux and Mac, configuring SSH is very simple. In the case of Windows, as we have indicated in the previous point, it is an indispensable condition that users use an SSH client.

SSH Linux server

If you wonder how to install [SSH Linux], the first thing you should do is access your terminal program and follow the following procedure. Type the [SSH command] correctly:

ssh {user} @ {host}

We will explain what this [SSH command] is step by step. On the one hand, {user} refers to the user account you want to access.

If you want to log in as a system administrator, you must indicate in the {user}, {root} section; In this way, you will have full freedom to make any modification in the system.

Install SSH server

To install an [SSH server], it is best to use OpenSSH. One point to keep in mind is that in the vast majority of Linux systems this server is already available by default.

Therefore, to install it you have to give the order to your package manager.

It recommends that you use apt-get under the Ubuntu Server 12.04 LTS distribution. You must execute the following command.

• sudo apt-get update
• Sudo apt-get install ssh

This way, you already have the [SSH server] installed. To verify that the process has been carried out successfully. It is best to try to establish a connection with the local computer. You must do it as follows: ssh user @ localhost.

SSH ports

Currently, almost 100% of servers use Linux as an operating system thanks to the support and stability it offers.

That is why cyberattacks against these servers are becoming more frequent. Thus, it is necessary to strengthen its security to avoid any unauthorized access.

A fantastic way to improve security on Linux servers is to change the [SSH port] used by the administrator to authenticate using the [SSH protocol]. The truth is that changing the [SSH port] is a very simple process. We explain it step by step.

• You must first edit the ssh_config file. To do this you must use the following command: nano / etc / ssh / sshd_configure for what you just installed the command line text editor for Linux.
• Once it executes the command, look for the line that says “#Port 22 ”. So, what you should do is change the 22 to the number of the port you want to configure. Also, you have to delete the #.
• Then save all the changes you have made. To do this, press the Control and X keys at the same time.
• The next step is to restart this service with the following command: /etc/init.d/ssh restart.
• From that moment, you will already make all the connections with the port you have chosen.

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