What is a Firewall?

All of us have had experience with firewalls at some point or another but what exactly are firewalls and how do they work? Firewalls are programs (or sometimes hardware devices) that are used to filter information coming from the internet to a private network or computer. This means that a computer doesn’t have a direct path to the internet; instead the computer and the material have to pass through the firewall, which will sort out anything it deems harmful to the system.

These programs are customizable and so the firewall can be told what to let through and what to block. As such, firewalls are often used by corporations who have hundreds upon hundreds of computers to manage. Instead of installing software on every individual computer on the network, the company can use a firewall which has many of the same benefits. What firewalls are best at is protecting networks or computers from anyone who would want to remotely access them. However, there are still many ways that a computer can be vulnerable which is why many firewalls are paired with antivirus software. 

Sources
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http://computer.howstuffworks.com/firewall.htm

http://www.teach-ict.com/as_a2_ict_new/ocr/AS_G061/317_role_impact_ict/ict_crime/miniweb/pg9.htm