What is SSH?

SSH, also known as Secure Shell or Secure Socket Shell, is a network protocol that gives users, particularly system administrators, a secure way to access a computer over an unsecured network. SSH also refers to the suite of utilities that implement the SSH protocol. Secure Shell provides strong authentication and encrypted data communications between two computers connecting over an open network such as the internet. SSH is widely used by network administrators for managing systems and applications remotely, allowing them to log into another computer over a network, execute commands and move files from one computer to another.

In fewer words, SSH is a protocol that allows two machines to communicate securely. A client connects into a server, in a similar way to how your browser connected to a server to receive this content before displaying it on your screen. SSH secures traffic by encrypting it. Other protocols, like Telnet and HTTP, do not. As you likely know, HTTPS does, which is why it is preferred over HTTP.

SSH refers both to the cryptographic network protocol. SSH uses the client-server model, connecting a secure shell client application, the end at which the session is displayed, with an SSH server, the end at which the session runs. SSH implementations often include support for application protocols used for terminal emulation or file transfers. SSH can also be used to create secure tunnels for other application protocols, for example, to securely run X Window System graphical sessions remotely. An SSH server,
by default, listens on the standard Transmission Control Protocol (TCP) port 22.