Firewall Overview

Firewalls are filters that stand between a computer or computer network and the Internet. Each firewall can be programmed to keep specific traffic in or out. All messages passing through the firewall are examined and those not meeting pre-defined security criteria are blocked.

For example, on the outbound side, firewalls can be configured to prevent employees from transmitting sensitive data outside the network, while on the inbound side, firewalls can be configured to prevent access to certain kinds of websites like social media sites.

Some of Firewall methods

Firewalls use several methods to control traffic flowing in and out of a network:

• Packet filtering: This method analyzes small pieces of data against a set of filters. Those that meet the filter criteria are allowed to pass through, while others are discarded.
• Proxy service: In this method, computers make a connection to the proxy which then initiates a new network connection based on the content of the request. In this way, there is no direct connection or packet transfer on either side of the firewall. Network addresses are effectively hidden.
• Stateful inspection: Stateful inspection is the new standard firewall security method that monitors communications packets over a period of time. Outgoing packets that request specific types of incoming packets are tracked. Only incoming packets that are an appropriate response are allowed to pass. Firewalls using this method are often referred to as next-generation firewalls (NGFW).