How Do Firewalls Work? Basic Firewall Fundamentals

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Firewalls are physical or digital systems that filter data before it is allowed access to a computer, protecting devices from cyberthreats, such as dangerous programs or malicious code. 

See below to learn all about how firewalls work in the market:

Firewall technology

A firewall keeps unwanted data and traffic from accessing networks and devices. 

There are different operating methods for firewalls. Network administrators choose the combination of technology and methodology best suited to their needs, whether prioritizing speed or security or a certain-type of application.

Hardware and software firewalls

The two main types of firewalls are hardware and software. The main difference between the two is that a hardware firewall is separate from the device or devices it is defending, while a software version is integrated into them.

Firewalls can also be sorted into network-based and host-based versions. Either can be hardware or software, though it generally makes more sense for network-based firewalls to be hardware rather than software. For example, most Wi-Fi routers have a network-based hardware firewall built into them.

A network-based firewall is designed to protect all of the devices running on a certain network. In contrast, a host-based firewall concentrates on protecting only one specific device. In this case, it makes sense for a host-based firewall to be software, although it can also be hardware.

Firewall policies and rule sets

If network security were broken down into layers, firewall policies and rule sets would form the crucial outermost layer. These are the underlying laws firewalls live by. They tell it what traffic to allow and what to deny or drop.

A firewall’s policy comprises rule sets that outline traffic from specific applications or sources to deny or allow. It may be helpful to think of this in terms of a real-world law. 

See more: Why Firewalls are Important for Network Security

Firewall types

These are some the key ways that firewalls operate in as a network security solution:

Packet-filtering firewall

With packet filtering, the firewall filters incoming data packets, comparing them against known malicious types. If it can pass through each filter successfully, it is allowed to enter the network or device. The data packet will be dropped or denied if any of the filters detect red flags, such as a malicious file type.

Proxy service firewall

A proxy service firewall creates a simulated version of the computer receiving the incoming data. The firewall acts as the computer itself, so incoming information doesn’t interact with the actual one. If anything ends up being harmful, it can’t do anything, because it only reaches the firewall, not the network or devices beyond.

Proxy service firewalls are among the most secure, but they operate slower than other types and are more difficult to scale.

Stateful inspection firewall

A stateful inspection firewall is similar to a packet-filtering one. It examines incoming data packets more closely than standard packet filtering, looking at numerous characteristics. Incoming data packets are compared against a database of trusted and malicious data. Stateful inspection firewalls also record traffic, building on their directories.

Understandably, stateful inspection firewalls require more processing power and data storage resources than other types. It can pay off through their more in-depth security inspections.

Application firewall

An application firewall can use any of the above security types. However, they are designed specifically for a certain application or type of traffic. The most well-known is a web application firewall, which filters HTTP traffic.

See more: How Firewalls are Used by Deakin University, Black Box, Palo Alto Networks, Modis, and Keysight: Case Studies

Core functionality of firewalls

The primary purpose of a firewall is to defend against harmful data. Different configurations will do that best for various users and applications.

Large companies

It is common for large businesses to use network-based hardware firewalls and multiple versions for different segments of their network. One of the drawbacks of hardware firewalls is that they typically require dedicated, knowledgeable personnel to operate and maintain. Big companies have the resources to have a technician as part of their security team.

Network-based firewalls are usually the best option for large businesses, since they can cover multiple devices under a shared set of policies and rule sets. Some big companies will segment their networking and use different firewalls for each segment based on the security needs throughout the organization. Colleges and universities commonly use this strategy.

Large organizations can implement various firewall technologies. For example, a university might keep the campus coffee shop on a standard packet filtering firewall, while the administrative offices are on a more secure proxy service firewall or stateful inspection firewall.

See more: What is a Firewall? Definition, Features, and Types

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