Ubuntu - Ping - Disable ping

You can disable all ICMP traffic on a linux machine, by the following method.

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

The above method is only temporary. In fact anything you modify inside /proc will only stay until the reboot.

To make that permanent, you need to add the below line in /etc/sysctl.conf file.

/etc/sysctl.conf

net.ipv4.conf.icmp_echo_ignore_all = 1

Doing a TCPDUMP on the machine, with icmp disabled will show you only echo_requests, because all ICMP request are ignored by the machine (No reply of any kind, so there is no mechnism to know whether its dropped or not).

tcpdump -v icmp

result:

tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 96 bytes
02:50:51.827077 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 192.168.0.102 > 192.168.0.103: ICMP echo request, id 34826, seq 11, length 64
02:50:52.827101 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 192.168.0.102 > 192.168.0.103: ICMP echo request, id 34826, seq 12, length 64
02:50:53.826859 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], proto: ICMP (1), length: 84) 192.168.0.102 > 192.168.0.103: ICMP echo request, id 34826, seq 13, length 64