Which service is provided by TCP port 23?

The service provided by TCP port 23 is Telnet. Telnet is a network protocol that allows for command-line interface access to remote devices over a network. It operates in a client-server model where the Telnet client, running on a user’s device, connects to a Telnet server on a remote device.

Telnet is primarily used for managing devices like routers, switches, and servers, allowing administrators to execute commands as if they were physically present at the device. Despite its usefulness, Telnet transmits data in plain text, including usernames and passwords, which poses security risks. This is one reason why many organizations have shifted to using more secure alternatives, such as SSH, which operates on TCP port 22 and encrypts the data being transmitted.

Other choices correspond to different services: SSH, which provides secure shell access, operates on a different port and encrypts data; FTP, which is used for file transfers, primarily operates on ports 20 and 21; and HTTPS, which is a secure version of HTTP, typically operates on port 443. Understanding the specific ports associated with different protocols is essential for network administration and security practices.