Telnet is a xinetd managed service which listens on port 23. You can login to your account on the server by using a telnet client. However, unlike ssh, telnet initiates a normal connection. i.e., the telnet data packets is in plain-text format, and can be captured easily by network monitoring applications.
If you are a system administrator managing a server, it is compulsory that you have telnet service disabled on it. This is how it is done:
1. Login to your server through SSH and su to root.
3. Look for the line:
disable = no
and replace with
disable = yes
4. Now restart the xinetd service:
5. Turn off it through chkconfig as well because it can still start during the next reboot.
/sbin/chkconfig telnet off