The command which you are entering is just for blocking incoming ICMP connection if you want to block outgoing ICMP connection you have to choose output chain i.e
`sudo iptables -A OUTPUT -p icmp -j DROP`
The command which you are entering is just for blocking incoming ICMP connection if you want to block outgoing ICMP connection you have to choose output chain i.e
`sudo iptables -A OUTPUT -p icmp -j DROP`