The easiest way of disabling ICMP echo request on Linux is doing it on the kernel level.
To disable ICMP immediately on a running system, simply enter the following command :
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all
This command will not survive to the next reboot. To make it permanent, edit :
vi /etc/sysctl.conf
And add :
net.ipv4.conf.icmp_echo_ignore_all = 1
You can also achieve this through IPtables. Just edit :
/etc/sysconfig/iptables
And add :
iptables -I INPUT -p icmp --icmp-type 8 -j DROP
And for IPv6 :
ip6tables -I INPUT -p icmpv6 --icmp-type 8 -j DROP