To disable telnet service on a system, which action should you take?

A.
Put NONE in /etc/telnet.allow

B.
Remove the appropriatetelnet init script.

C.
Put a line ‘ALL:ALL’ in /etc/hosts.deny

D.
Comment the telnet entry in /etc/inittab

E.
Comment the telnet entry in /etc/inetd.conf

Explanation:
inetd, called also the super server, will load a network program based upon a request from the network. The inetd.conf file tells inetd which ports to listen to and what server to start for each port.

The first thing to look at as soon as you put your Linux system on ANY network is what services you need to offer. Services that you do not need to offer should be disabled and uninstalled so that you have one less thing to worry about, and attackers have one less place to look for a hole. Look at your /etc/inetd.conf file to see what services are being offered by your inetd program. Disable what you do not need by commenting them out by adding a # at the beginning of the line, and then sending your inetd process a SIGHUP command to update it to the current inetd.conf file.

Example from /etc/inetd.conf:
# telnet stream tcp nowait root /usr/sbin/tcpd in.telnetd

Hints:
use this command to signal inetd to reload its config file:
# killall -HUP inetd
use this command to make inetd.conf immune to accidental, or otherwise, changes:
# chattr +i /etc/inetd.conf