Stop being pinging by any host

Edit /proc/sys/net/ipv4/icmp_echo_ignore_all
[root@vikas ]# echo "1" > /proc/sys/net/ipv4/icmp_echo_ignore_all
[By doing this no body can ping you]

or

EDIT sysctl.conf
add these lines:
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.icmp_echo_ignore_all=1
[check]
sysctl -p