How a Firewall Works

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In April 2017, Michael Marlowe became the director of strategy and vice president of new markets for ChaseTek in Columbus, OH. Michael Marlowe serves the Columbus, OH, company by identifying and acting on growth opportunities in the management of infrastructure and elements of such infrastructure, including firewalls.

As its name indicates, a firewall functions as a protection against unwanted and potentially dangerous information coming into a network. It serves the dual purpose of preventing users outside of a private network from accessing protected resources, while simultaneously screening the information that its own users can encounter.

Network traffic approaches a firewall in a container known as a packet. Each packet includes a control header, which contains such key information as the destination and source of the packet’s data payload. Depending on its construction, the firewall may exclusively use the control header or examine the contents of the packet to determine whether it should let the information through.

A firewall evaluates each set of data using a sequence of pre-set rules. As soon as the firewall identifies a rule that applies to the incoming information, it applies the associated action. If there is no applicable rule, the firewall applies a default action.

One of three things can happen to any incoming packet of data, the first being the data’s acceptance and passage through into the network. If the firewall chooses to block the traffic, however, it can send a reply to the sender that the recipient is unreachable. In some cases, however, the designer of the firewall can choose to disallow the passage of data with no reply to the sender.