Which protocol is most commonly used for establishing secure connections for remote command line access?

The most commonly used protocol for establishing secure connections for remote command line access is SSH (Secure Shell). SSH is specifically designed to provide a secure channel over an unsecured network in a client-server architecture. It encrypts the data transmitted between the client and server, which protects against eavesdropping and man-in-the-middle attacks. This ensures that sensitive information like passwords and commands are not exposed during transmission.

Additionally, SSH supports various authentication methods and can also provide secure tunneling for other protocols, enhancing its versatility for remote administration tasks. In environments where security is a priority, such as system administration and network management, SSH is the standard choice due to its robustness and security features.

In contrast, Telnet does not provide encryption and transmits data in plain text, making it a less secure option for remote access. FTP (File Transfer Protocol) is mainly used for transferring files and does not incorporate security features, while HTTPS (Hypertext Transfer Protocol Secure) is primarily used for secure communication on the web rather than for command-line access. Therefore, SSH stands out as the appropriate choice for secure remote command line access.