SSH
Secure Shell - a cryptographic network protocol for secure remote access and command execution over unsecured networks.
SSH (Secure Shell) is a cryptographic network protocol that provides a secure channel for remote login, command execution, and data transfer between computers over an unsecured network. It replaces older, insecure protocols such as Telnet and rlogin by encrypting all traffic between the client and server. SSH uses public-key cryptography for authentication and supports password-based, key-based, and multi-factor authentication methods. Beyond remote shell access, SSH enables secure file transfers via SCP and SFTP, port forwarding, and tunneling. OpenSSH is the most widely used implementation and comes pre-installed on nearly all Linux distributions. SSH typically operates on port 22 and is a fundamental tool for system administrators managing remote servers.