How do I configure a machine to respond or not respond to ping requests?

Question

How can I manage my Ubuntu machine so it doesn't (or does) respond to PING (ICMP ECHO_REQUEST - type 8) requests?

Normally almost all computers in a LAN network respond to ping with an ICMP ECHO_REPLY, but how to turn it off?

How to manage it? How to manage other types of ICMP requests?

Answer 1

Another option (not using a firewall) is to set a Linux kernel option.

As most things are accessed as files in Linux, kernel settings are mapped into the special /proc file system

echo 1 | sudo tee /proc/sys/net/ipv4/icmp_echo_ignore_all

you can also make this permanent by setting the value in the file /etc/sysctl.conf:

net.ipv4.icmp_echo_ignore_all = 1

then execute sysctl with -p flag to activate

sudo sysctl -p

Answer 2

You can this through two methods: using ufw or iptables.

Using UFW

You need to add:

-A ufw-before-input -p icmp --icmp-type echo-request -j DROP

to:

/etc/ufw/before.rules

then run:

sudo ufw disable
sudo ufw enable

Using iptables

Add the following rules:

iptables -A OUTPUT -p icmp -o eth0 -j ACCEPT          
iptables -A INPUT -p icmp --icmp-type echo-reply -s 0/0 -i eth0 -j ACCEPT     
iptables -A INPUT -p icmp --icmp-type destination-unreachable -s 0/0 -i eth0 -j ACCEPT  
iptables -A INPUT -p icmp --icmp-type time-exceeded -s 0/0 -i eth0 -j ACCEPT       
iptables -A INPUT -p icmp -i eth0 -j DROP