A junior technician can log in to a legacy network switch from her workstation by typing telnet 192.168.5.10 at the command prompt. Because this traffic is sent in clear text, the security team wants to block only this specific remote-access service at the perimeter firewall while allowing all other services to remain available. Which TCP port must be denied to accomplish this task?
Telnet provides remote command-line access but transmits all data, including credentials, in plain text. Telnet sessions use TCP port 23. Blocking inbound and outbound traffic on TCP 23 prevents new Telnet connections to devices on the network without affecting services that rely on other ports, such as SSH (TCP 22), DNS (UDP 53), or Remote Desktop Protocol (TCP 3389).
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How does TCP port 23 differ from TCP port 22?
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