What Is SSH?
Secure Shell as an Encrypted Remote Login
SSH, short for Secure Shell, is a network protocol that lets you log in to and control a computer over an encrypted connection. It is the standard way administrators manage Linux servers from a distance, and the same secure channel also carries file transfers and version-control traffic.
Before SSH became common, remote login was done with tools such as Telnet, which sent everything, including passwords, as plain text that anyone on the network path could read. SSH runs a similar kind of session inside strong encryption, so observers see only scrambled data.
SSH uses a client-server model. The client is the program on your computer, such as the OpenSSH client included with most operating systems. The server is the SSH service on the remote machine, which normally listens on TCP port 22. A port is a numbered entry point on a machine, and 22 is the default for SSH, although administrators can change it. File transfers over SSH are covered in the article on SFTP and FTP.
How the Connection Is Protected and Verified
When a connection starts, the client and server agree on encryption methods and create shared session keys through a key exchange. The exchange is designed so that someone watching the traffic cannot recover those keys. Once it is complete, everything sent in the session is encrypted.
The server also proves its identity with a host key. The first time you connect, your client records that key. On later connections, it checks the key again and warns you if it has changed, which helps reveal a server that has been replaced by an impostor. The user then authenticates, most commonly with a password or with a key pair, which is explained in the article on SSH keys.
What SSH Access Means on a Hosting Plan
A hosting plan with SSH access gives you a remote command prompt on your account. From there you can manage files, check logs, run scripts or install tools without using a browser-based control panel. Many shared hosting plans offer SSH with a restricted set of commands, while VPS plans usually give more freedom.
SSH access does not mean full control of the server. It is limited to the permissions of the account you log in with, and your host decides whether SSH is offered, which shell you receive and what it can do. The commands you can run are described in the article on shell and Bash.
Frequently asked questions
Why Does SSH Use Port 22?
Port 22 is the default port assigned to the SSH service, so clients try it unless told otherwise. Because automated scanners check this port constantly, administrators often change the port or restrict access by network address. A different port does not replace strong authentication, however.
Is SSH Safe to Use Over the Internet?
SSH is designed for use over untrusted networks, because its encryption protects the session contents and its host keys help you verify the server. Its real-world safety also depends on configuration, such as how users authenticate and whether the software is kept up to date. Hardening is a separate topic, but the protocol itself is well established.