SSH, or Secure Shell, is a cryptographic protocol used to securely access and manage remote servers. It provides encrypted communication over potentially insecure networks, allowing administrators and developers to log in, run commands, and transfer files safely. SSH replaced older insecure protocols like Telnet by ensuring that credentials and data cannot be intercepted. It is a foundational tool in DevOps, backend development, and cloud operations. SSH connections authenticate users through passwords or, more commonly, cryptographic keys. Once connected, users gain a command line interface to the remote machine’s shell.
How it works
When initiating an SSH connection, the client and server perform a handshake to agree on encryption algorithms and verify identities. Public key authentication uses a private key stored locally and a matching public key placed on the server. SSH sessions allow port forwarding, which tunnels network traffic securely through the connection. Tools like scp and sftp run over SSH to move files between systems. SSH logs help track access attempts and security events. Proper key management and firewall rules are essential to securing SSH access.