CompTIA Linux+ XK0-006 (V8) Practice Question

The correct answer is Telnet. The Telnet protocol, which traditionally uses TCP port 23, transmits all data, including usernames and passwords, in clear text. The scenario described, with plaintext credentials on port 23, is a classic indicator of an active Telnet service. The best practice is to disable Telnet and replace it with SSH (Secure Shell), which encrypts the entire communication session. SSH is the secure alternative for remote command-line access, protecting credentials and data from being intercepted. FTP is also an insecure protocol that transmits credentials in plaintext, but it is used for file transfers and typically operates on ports 20 and 21. SFTP is a secure file transfer protocol that runs over SSH and would not exhibit this vulnerability.