Firewalls

= Firewalls =

Definition
toc A firewall is a device or program designed to protect a computer or network of computers from being accessed and/or damaged by outside sources, particularly threats originating from the internet. A firewall works as a barrier between the computer (or system) and the internet, filtering information that is being sent or retrieved from one to the other.

Image Source: How Firewalls Work, HowStuffWorks.com, Computer Networking Image Gallery

The person or group in charge of the computer or system must decide which types of information will be needed (i.e. email, full internet access), and by which users, as well as what should be blocked, in order to effectively implement a firewall. The person or group must also realize that firewalls cannot protect a system from several types of threats, such as viruses sent through emails or internal users who purposefully (or inadvertently) share sensitive data.

Firewalls can use packet filtering,proxy service, or stateful inspection to control the data being sent and retrieved. Firewalls can be programmed to allow, or not allow, information through that originates from certain IP addresses or domain names, or that contains certain words or phrases. They might also be set up to allow or block certain protocols, such as TCP,HTTP, FTP, UDP, ICMP, SMTP, etc.

Resources
For a more extensive explanation of firewalls, see Rob Pickering's Internet firewall tutorial.

PCWorld provides news, reviews, links to vendors, how-to guides, and other (some sponsored) information on firewalls (search "firewall").

In The Educated Shopper's Guide to Firewalls, J.M. Ivler provides information to help users determine the specific needs for their particular firewall system.

**References**
Ivler, J.M. (1996) The Educated Shopper's Guide to Firewalls. //Web Developer//, 2(1). Retrieved from http://webdeveloper.internet.com/security/security_shoppers_guide_firewalls.html

PCWorld. Retrieved from http://www.pcworld.com.

Pickering, R. Internet firewall tutorial. ipcortex. Retrieved from http://www.ipcortex.co.uk/wp/fw.rhtm

Tyson, J. How Firewalls Work. Howstuffworks. Available at: http://computer.howstuffworks.com/firewall.htm