Which of the following service allows a user to log in to another computer somewhere on the Internet?

Question

Which of the following service allows a user to log in to another computer somewhere on the Internet?

1. A. e-mail
2. B. UseNet
3. C. Telnet (Correct answer)
4. D. FTP

Correct Answer

Option C — Telnet

Detailed Solution & Explanation

The correct answer is Telnet.

Key Points

• Telnet is a network protocol that lets a user log in to and operate a remote computer over a network as though seated at it.
• It works on a client-server model and traditionally uses port 23.
• Because Telnet transmits data — including passwords — in plain text, it has largely been replaced by SSH, which encrypts the session.
• FTP transfers files, e-mail exchanges messages and UseNet is a discussion system; none provides remote login.

Additional Information

• Telnet runs on port 23 and transmits everything, including passwords, in plain text — which is why it is now considered obsolete for any network that is not fully trusted.
• Its secure replacement is SSH (Secure Shell) on port 22, which provides the same remote-login capability over an encrypted channel.
• Telnet still survives as a diagnostic tool for testing whether a particular port on a remote host is open.