Telnet is used to access remote computers. It is basically a user command and an underlying TCP/IP protocol. With telnet it is possible to access your server. Also, when you will login and use Telnet your login information i.e. the username and the password will be displayed in clear text. This is the reason that it should be disabled on your dedicated server and replaced with SSH.
If you do not do this it would be a great risk for your Linux dedicated servers hosting and it is possible that your server will face problems in the near future. You should make sure that Telnet is disabled on your server so that your server is secure enough. The incoming messages on port 23 and the messages are also send to port 23.
Telnet can be disabled on the server with the steps which are mentioned below. Follow the steps to disable Telnet on your server :
1. Login to your server through SSH and su to root.
2. Type pico /etc/xinetd.d/telnet
3. Look for the line: disable = no and replace with disable = yes
4. Now restart the inetd service: /etc/rc.d/init.d/xinetd restart
5. Turn off it through chkconfig as well because it can still start through that.
/sbin/chkconfig telnet off
6. Scan your server to ensure port 23 is closed.
nmap -sT -O localhost
Also run ps -aux | grep telnet and if you find anything other than “grep telnet” as result kill the process.
If you have followed the steps correctly telnet is disabled on your server and you can be rest assured with the same.