Blocking ICMP ping requests in Ubuntu 20

Step 1:

Backup existing firewall rules

sudo cp /etc/ufw/before.rules /etc/ufw/before.rules_backup

Step 2 :

Actual task is to replace Accept with Drop in firewall rules as below

Step 3:

Run below sed command to find and replace

sudo sed -i '/ufw-before-input.*icmp/s/ACCEPT/DROP/g' /etc/ufw/before.rules

If firewall already enabled then use reload command . If not enabled then use enable command as follows

sudo ufw enable

or
sudo ufw reload