David is a freelance writer specializing in technology. He holds a BA in communication.
Have you ever wished you could access a computer in another place as easily as you could while you were sitting right at the keyboard? With SSH, you can manage servers across the room, across the hall and even across the world with the right software.
SSH stands for Secure Shell. You might have used a shell on Linux, Mac or Windows to directly control the computer, but SSH lets you run commands from other computers. This is especially useful for people managing remote servers, whether in a local data center or in another site.
For example, a system administrator might want to change the configuration of a cloud server's operating system in another city. With SSH, she can log in to her computer from anywhere, even from home, without having to physically be at the machine.
SSH was created by Tatu Ylonen at the Helsinki University of Technology in 1995 as an alternative to the existing Telnet application, which also offers remote access. Yonen developed SSH after a hacker broke into a computer remotely via Telnet. Ylonen founded a company called SSH Communications to develop SSH, but the most common version in existence is an open source variant called OpenSSH, developed by the OpenBSD team. OpenBSD is an operating system known for its high security.
If you use Mac OS or Linux, you already have SSH on your system. If you use Windows, you can download an application called PuTTY to install SSH on your machine.
SSH aims to make remote connections to computers much more secure than using Telnet.
SSH does this by encrypting, or scrambling, the connection between your computer and the remote computer. With a Telnet connection, if a hacker manages to intercept the connection, it will be possible to read everything sent between the computers. This includes usernames and passwords. The hacker will then be able to get into the machine and see everything on it. This could be a website, a database, even credit card information.
While in most cases you'll only be able to access text applications over the command line, on Unix/Linux systems, it's also possible to access graphical applications remotely with the right settings, though this is slower than using them directly on the desktop. For example, a college computer lab could share a copy of a graphical scientific program running on a central server, such as Mathematica, using a site license.
The ability for system administrators to remotely log in and make changes to the operating system and applications, such as databases and web servers, makes SSH a very valuable tool for anyone in IT.
With SSH, a hacker will only see gibberish over the connection, which keeps important data safe.
SSH has other methods beside encryption of keeping data safe. It usually prohibits users from logging in as root. On Unix and Linux systems, root, or superuser, has access to every file and setting on the system. If a hacker got a hold of this account, he or she could lock other administrators out, delete files or steal information. It's, therefore, very important to keep this account secure and limit access as much as possible.
SSH also allows users to access the computer using public key authentication. With public key cryptography, if a private key matches a public key known to the system, the user is granted access. This offers even more security by making sure that authorized users are who they say they are and not hackers who are stealing or guessing passwords. It's even possible with public key to log in without a password at all.
A user who doesn't want to remember a password can upload a public key into a certain place in the home directory and will be able to log in without a password. A user who wants more security will still want to use a password. It's also possible to use a longer, more complex password known as a passphrase for extra security.
SSH, or Secure Shell, makes it very easy to access remote servers while keeping them safe from hackers. SSH uses encryption to keep the connection between a user and a remote computer secure. It also uses public key encryption to add even more security while giving the option to eliminate passwords entirely.
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