Install firewall-applet by entering the following commands in the terminal:
sudo apt update sudo apt install firewall-applet
Description:
panel applet providing status information of firewalld
firewalld is a dynamically managed firewall daemon with support for network/firewall zones to define the trust level of network connections or interfaces. It has support for IPv4, IPv6 firewall settings and for ethernet bridges and has a separation of runtime and persistent configuration options. It also provides a D-Bus interface for services or applications to add and apply firewall rules on-the-fly. . This package provides a panel applet which shows status information of firewalld.
Homepage: http://www.firewalld.org/
Version: 0.4.4.6-1
Section: universe/net