Which of the following protocols would be BEST used to access the command line interface of a router securely?

Telnet transmits all data including passwords in plaintext over TCP port 23, making it completely insecure for remote device management.

HTTP is a web application protocol used to serve web pages and does not provide a command line interface or encrypt session data.

SSH establishes an encrypted tunnel between the client and the network device, protecting all transmitted data - including usernames, passwords, and commands - from interception. It operates on TCP port 22 and supports strong authentication methods including public-key cryptography. SSH replaced Telnet specifically because Telnet transmits everything in plaintext, making SSH the universally accepted standard for secure remote CLI management of network devices.

SFTP (SSH File Transfer Protocol) is used for secure file transfers over an SSH connection and does not provide interactive CLI access to a device.