Environment: CentOS 5, 7

You can use the following command to test before disabling:

ping 192.168.241.2   #Replace with your own IP

Disable Ping (Temporary, for when rebooting the host is inconvenient)

The command is as follows (takes effect immediately, but will be reset after a restart):

echo 1 >/proc/sys/net/ipv4/icmp_echo_ignore_all

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Permanently Disable Ping

Add the command to run automatically at startup or reboot:

For CentOS 5, add on startup:
vi /etc/rc.d/rc.local  #Edit the startup file and add the following command
echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all

For CentOS 7, add on startup:
echo "net.ipv4.icmp_echo_ignore_all=1" >> /etc/sysctl.conf

sysctl -p #Apply immediately

You can combine the temporary and permanent methods. Test the result after completion.

How to Enable: Allow Ping

Simply change the 1 to 0 in the commands above:

echo 0 >/proc/sys/net/ipv4/icmp_echo_ignore_all

For CentOS 5, remove from startup:
vi /etc/rc.d/rc.local  #Edit the startup file, delete the following
echo 0 > /proc/sys/net/ipv4/icmp_echo_ignore_all

For CentOS 7, remove from startup:
vi /etc/sysctl.conf #Edit the startup file, delete the following
net.ipv4.icmp_echo_ignore_all=0

sysctl -p #Apply immediately