CompTIA Server+ SK0-005 Practice Question

The correct answer is an active Telnet service. TCP port 23 is the well-known port for the Telnet protocol, which transmits data, including credentials, in cleartext and is considered a security risk. An active service is required to bind to a port and place it in a LISTENING state. A firewall rule may permit traffic to a port, but it does not cause the port to listen for connections; only an active service or application can do that. A zombie process is a terminated process whose entry remains in the process table but does not actively hold resources like a listening network socket. The hosts file is used for local hostname-to-IP address resolution and has no role in opening network ports.