CompTIA Linux+ (XK0-004) — Question 268

After running an Nmap scan on a local area network, a penetration tester notices several older Linux servers have port 23 open. Which of the following should the systems administrator do as a security best practice?

Answer options

• A. Use a non-standard port for Telnet.
• B. Disable and uninstall the Telnet service.
• C. Ensure the kernels are up to date with the latest patches.
• D. Configure the firewall to allow Telnet access only from trusted networks.

Correct answer: A

Explanation

Using a non-standard port for Telnet (option A) can help obscure the service from attackers, thus enhancing security. Disabling and uninstalling the Telnet service (option B) is also a good security practice, but if Telnet is still needed, changing the port is a better immediate step. Keeping kernels updated (option C) is important, but it does not directly address the specific vulnerability of having Telnet open. Configuring the firewall (option D) is beneficial, but does not eliminate the risk associated with an open Telnet service.