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Term of the Week: Firewall

What is it?

A network security system built into hardware or software that monitors network traffic and controls incoming and outgoing traffic based on a set of rules.

Why is it important?

Firewalls enable system administrators to monitor and control network traffic coming into and out of their systems. Firewalls provide a first line of defense against network-based cybersecurity attacks. They are also used to censor information by blocking traffic to and from certain sites.

Why does a business professional need to know this?

Firewalls first came into use as packet filters that analyzed data in packets and identified which data was safe to continue moving forward and which data needed to be removed or stopped. Up to that point, network administrators had to choose between keeping networks connected to the internet, allowing most data to come and go, or disconnecting networks completely, leaving them physically isolated.

Modern firewalls work in hardware and software through an established set of rules to determine what comes in and what goes out. Firewalls are considered a first line of defense against unwanted intruders, information, or code. They can be used to keep out hackers or merely to cut down on spam.

Two common types of firewalls are network firewalls, which monitor and filter communications between networks (e.g., between an internal corporate network and the external internet), and host-based firewalls, which monitor and filter communications coming in and out of an individual computer. A firewall can block a communication packet based on the port it attempts to pass through or the type of content it contains.

The most famous firewall is the Great Firewall of China(Great Firewall of China), which the Chinese government uses to block people inside China from accessing sites and services containing information prohibited by the government. Google, for example, is blocked in China, so Chinese internet users generally must use the Chinese internet search engine Baidu, which operates through censorship filters. The Chinese firewall has been surprisingly successful at blocking vast amounts of information.


  • (Great Firewall of China) The Great Firewall of China: Comparatec. Online tool designed to determine whether a website (or other internet content) is available to those who reside in China.

About Sarah Granger

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Sarah Granger is a former network security engineer and author of The Digital Mystique: How the Culture of Connectivity Can Empower Your Life – Online and Off. She previously contributed to two books on cybersecurity: Diplomacy, Development and Security in the Information Age and Ethical Hacking.

Term: Firewall



Twitter: @sarahgranger



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