10. Firewalls

A firewall is a hardware device or a software application that sits between the internal network of the organization and external networks in order to protect the internal network from communicating with the outside networks. A properly configured firewall blocks all unauthorized access to the internal network and also prevents internal users from accessing potentially harmful external networks. The three common firewall technologies are packet-filtering firewalls, Application layer firewalls, and State full Inspection Firewalls.