What is a firewall?
Simply put, a firewall is any device or application that is capable of blocking or permitting information that is passing through it.
Firewalls come in two main forms:
- Physical devices that are connected, most often, on an Internet connection, between the Internet service provider and any devices that need to be protected, such as computers, servers, or other devices on a company’s network.
- Virtual devices or applications that are used to protect the system, such as a server, that it is installed on.
On the more basic firewall there may be a simple set of allow/deny rules that can be compared to an intersection. Information moving through a firewall is called a packet, which can be thought of like a vehicle moving through an intersection. The rules on a firewall can be thought of as the stop signs or traffic lights in the intersection. Careful planning of the lights and signs is required to safely move vehicles through the intersection much like rules on a firewall need to be carefully planned to ensure only information that should pass through the firewall in the necessary direction. In a simple firewall, it doesn’t matter what information is carried within the packet, much like it doesn’t matter what is inside a vehicle moving through an intersection.
At the other end of the spectrum you will find extremely complex firewalls, with multiple sets of detailed rules and configurations that are more closely related to vehicles moving through customs at an international border. There are complicated rules that govern what is and isn’t allowed, as the information moving through the firewall will be looked at down to the 1’s and 0’s that are used to represent the information. Inspection is performed on cargo, people, and vehicles that pass through a border – there may be nothing wrong with a vehicle or the people inside, but if one illegal item is found, the entire vehicle is stopped and not allowed to proceed. This is the same for the packets moving through a firewall – most of the information within the packet may be ok, but a tiny set of it may be deemed not permitted, and all the information within the packet is stopped and discarded.
Diligence when selecting a type of firewall, crafting the rules that govern the information flowing through the firewall, and ongoing maintenance of the firewall’s software is critical to maintaining the security of a business’ information.
