A Firewall is a network security device that monitors and filters incoming and outgoing network traffic based on an organization’s previously established security policies. At its most basic, a firewall is essentially the barrier that sits between a private internal network and the public Internet. There are three basic types of firewalls that are used by companies to protect their data & devices to keep destructive elements out of network, viz. Packet Filters, Stateful Inspection and Proxy Server Firewalls. Firewalls provide protection against outside cyber attackers by shielding your computer or network from malicious or unnecessary network traffic. Firewalls can also prevent malicious software from accessing a computer or network via the internet.