You should NEVER leave this port open on a server accessible from the internet. It is notoriously insecure. If you need to remotely access a server, use port 22 (ssh). What? Your OS doesn't support sshd? In that case, I suggest switching to a real OS.
keep in mind that the port number does not determine everything. running a telnet server and allowing it to be open to the public is bad, especially on port 23. it is merely a strong suggestion to run certain services on certain ports. i am frankly angry that security scores about my LAN that i submit are very bad because i have port 23 open and respond on it, but i am merely running ssh on port 22 which gets switched to port 23 as it goes through my by-hand configured firewall. i'm doing this because i have several computers running ssh on them that i want accessible from the internet. although most of the time (especially from inexperienced users), having port 23 open is a bad thing, its not always.
I too would like to know how to properly close port 23. If IS connected to my cable modem and closing it only prohibits remote desktop and XP assistance, is that necessarily a problem? It seems the need to close it outweighs that option....SO, how does one close this port 23?.....please?
Telnet on Mac OS X Because the Terminal application in Mac OS X can make Telnet and SSH connections, Mac OS X does not require a separate Telnet or SSH client, although you may still prefer to use one.
The queen of hacker commands is telnet. To get Windows help for telnet, in the cmd.exe window give the command:
Here's what you will get:
telnet [-a][-e escape char][-f log file][-l user][-t term][host [port]] -a Attempt automatic logon. Same as -l option except uses the currently logged on user's name. -e Escape character to enter telnet client prompt. -f File name for client side logging -l Specifies the user name to log in with on the remote system. Requires that the remote system support the TELNET ENVIRON option. -t Specifies terminal type. Supported term types are vt100, vt52, ansi and vtnt only. host Specifies the hostname or IP address of the remote computer to connect to.