Firewalls and Filtering Routers


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Firewalls and Filtering Routers
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What's a firewall?

To build a barrier between an internal network and the Internet, a company can install a firewall. The firewall becomes the only way anyone can access the network from outside. Because everything entering the network has to pass through the firewall, it controls all traffic between the network and everything outside it. Unauthorized users outside the network can't access information inside it, but authorized users can still travel outside the network to take advantage of Internet services.

How do firewalls work?

Firewalls use proxy software to build a wall between computers inside and outside the network. If you want to talk to a computer at another company's network, you really talk to the firewall while the firewall talks to the other computer. The firewall also talks to your computer for anyone outside your company's network. So, the firewall acts as a proxy for all traffic passing through it and can support a wide variety of communications software programs used for Internet navigation, like file transfer protocol (ftp) or telnet.

What's a filtering router?

Like a firewall, a filtering router is placed between the Internet and an internal network. Filtering routers only check the source and destination addresses on packets, the chunks of information sent across the Internet, to figure out if they should be let through. This prevents users on computers outside the network from fooling it into believing they're inside the network.