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What is a firewall and what does it do?

If you’re a geek/networking geek/hacker,  you’ve probably heard of firewalls.

The truth is that firewall software, which controls the flow of data into and out of a network, is present in the vast majority of household and commercial networks.

A firewall is an important security layer that acts as a barrier between private networks and the outside world. Firewall architectures have evolved dramatically over the last four decades, from first-generation, stateless firewalls to next-generation firewalls.

Learn the different types of firewalls, their differences, and how each type can protect your network in different ways.

What Are The Different Types Of Firewalls?
What Are The Different Types Of Firewalls?

The 5 Best Firewall For Home (TOP PICKS!)

What Does A Firewall Protect Against?


A firewall is a security tool that monitors incoming and/or outgoing network traffic in order to detect and block malicious data packets based on predefined rules, allowing only legitimate traffic into your private network.

Firewalls, whether implemented as hardware, software, or both, are typically your first line of defense against malware, viruses, and attackers attempting to gain access to your organization’s internal network and systems.

A physical or hardware firewall, similar to a walk-through metal detector door at a building’s main entrance, inspects each data packet before allowing it in. 

It looks for the source and destination addresses and decides whether or not to allow a data packet to pass through based on predefined rules.

Once a data packet enters your organization’s intranet, a software firewall can further filter the traffic to allow or deny access to specific ports and applications on a computer system, allowing for greater control and security against insider threats.

An access control list can specify which Internet Protocol (IP) addresses should not be trusted. Any data packets coming from those IP addresses will be dropped by the firewall.

Alternatively, the access control list can specify trusted-source IP addresses, and the firewall will only allow traffic from those addresses. There are several methods for configuring a firewall. The level of security they provide is also determined by the type of firewall and how it is configured.

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What are the 8 Different Types of Firewalls?

Firewalls are classified into eight types. Firewalls are classified into several types based on their general structure and mode of operation. Here are eight different types of firewalls. 

  • Packet-filtering firewalls
  • Circuit-level gateways
  • Stateful inspection firewalls
  • Application-level gateways (a.k.a. proxy firewalls)
  • Next-gen firewalls
  • Delivery Method Type Firewalls
  • Software firewalls
  • Hardware firewalls
  • Cloud firewalls
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What are the 8 Different Types of Firewalls?
What are the 8 Different Types of Firewalls?


1. Packet-Filtering Firewalls

The most “simple” and oldest type of firewall design, packet-filtering firewalls, effectively construct a checkpoint at a traffic router or switch.

Without opening the packet to check its contents, the firewall inspects information such as the destination and origination IP addresses, packet type, port number, and other surface-level information in data packets traveling through the router.

An information packet is dropped if it fails the examination. These firewalls have the advantage of not consuming a lot of resources. As a result, they have little influence on system performance and are quite straightforward.

When compared to the Best firewalls with more comprehensive inspection capabilities, they are, nonetheless, rather easy to defeat.

2.  Circuit-Level Gateways

Another simple firewall type is the circuit-level gateway, which operates by checking the transmission control protocol (TCP) handshake to swiftly and efficiently allow or prohibit traffic without requiring substantial computational resources.

The purpose of this TCP handshake check is to guarantee that the packet is from a valid session. While incredibly resource-efficient, these firewalls do not verify the packet itself.

As a result, if a packet included malware but had the correct TCP handshake, it would be allowed to flow. This is why circuit-level gateways alone are insufficient to secure your organization.

3. Stateful Inspection Firewalls

These firewalls use a combination of packet inspection technology and TCP handshake verification to give protection that neither of the previous two architectures could provide on its own.

These firewalls, however, put an additional burden on computing resources. When compared to the other options, this may cause valid packets to be transferred more slowly.

4.  Proxy Firewalls (Application-Level Gateways/Cloud Firewalls)

Proxy firewalls filter incoming traffic at the application layer between your network and the traffic source, hence the name “application-level gateway.”

These firewalls are provided via a cloud-based service or another proxy device. Instead of allowing direct connections, the proxy firewall connects to the source of the traffic first and inspects the incoming data packet.

Like the stateful inspection firewall, this check checks both the packet and the TCP handshake protocol. Deep-layer packet inspections, on the other hand, may be performed by proxy firewalls, which verify the actual contents of the information packet to ensure that it does not include malware.

Once the check is complete and the packet is approved to connect to the destination, the proxy sends it out. This creates another layer of separation between the “client” (the system from which the packet came) and the individual devices on your network, disguising them and providing your network with more anonymity and safety.

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If proxy firewalls have one negative, it is that the extra steps in the data packet transfer process can cause significant slowness.

5.  Next-Generation Firewalls

Many of today’s firewall products are promoted as having “next-generation” architectures. There is less agreement, however, on what constitutes a really next-generation firewall.

Deep-packet inspection (examining the data packet’s real contents), TCP handshake checks, and surface-level packet inspection are all typical elements in next-generation firewall systems. Other technologies, such as intrusion prevention systems (IPSs), which seek to automatically thwart network threats, may be included in next-generation firewalls.

The issue is that there is no uniform definition of a next-generation firewall, therefore it is vital to determine what precise capabilities are required before investing in one.

8 Types of Firewall Architectures
8 Types of Firewall Architectures

6.  Software firewalls

A host firewall, often known as a software-based firewall, is placed on a server or other device. Every device that needs to be protected must have host firewall software installed. As a result, software-based firewalls utilize some of the host device’s CPU and RAM resources.

Because of software-based firewalls, individual devices are well-protected against viruses and other dangerous content. They are capable of distinguishing between the many programs operating on the host and filtering inbound and outbound traffic.

This gives you fine-grained control by allowing you to allow communications to/from one program while limiting communications to/from another.

7. Hardware firewalls

A hardware-based firewall is a device that acts as a secure gateway between devices inside and outside of the network’s perimeter. Because hardware-based firewalls are self-contained appliances, they do not use the host device’s processing power or other resources.

These appliances, also known as network-based firewalls, are appropriate for medium and large businesses that require the protection of a large number of devices. Hardware-based firewalls require more configuration and management than host-based firewalls.

8. Cloud Firewalls

On the hand is a data cloud with a protective barrier for a cloud firewall. A cloud firewall or firewall-as-a-service is a firewall that is provided via a cloud solution (FaaS).

Many people mix up cloud firewalls and proxy firewalls because proxy servers are regularly utilized in proxy firewall configurations (though the proxy does not have to be on the cloud, it is frequently).

The primary benefit of employing cloud-based firewalls is their ease of scalability with your enterprise. As business needs change, you can increase the capacity of the cloud server to manage higher traffic volumes. Cloud firewalls, like physical firewalls, excel at perimeter security.

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Firewalls Used In-Network Environments

Firewalls are employed in both networked and non-networked environments. To safeguard their network, most firms use some sort of firewall, and many use or supply a combination of software and hardware firewalls.

A non-networked firewall functions similarly to a personal phone or DSL modem. Some gadgets, such as personal digital assistants or a home-owned PC/laptop, are, nonetheless, network-connected.

With either form of firewall, software and hardware firewalls are implemented as independent devices. This provides you with two alternatives for installing firewalls. You can employ both software and hardware firewalls.

A software firewall is created as a single program, although a hardware firewall functions similarly.

The sole distinction is that a hardware firewall is intended to be used in conjunction with one or more additional devices. The term “firewall” can refer to either the hardware or software firewall models.

CONCLUSION On The Different Types Of Firewalls

Choosing the appropriate firewall necessitates not only knowledge of the architecture and functions of the private network under protection, but also knowledge of the many types of firewalls and firewall policies that are most effective for the enterprise.

Whatever firewall(s) you choose, keep in mind that a misconfigured firewall might be worse than no firewall at all in some instances since it creates a dangerously false sense of security while providing little to no protection.

FAQ s About The Different Types Of Firewalls

Which firewall architecture is right for your business?

Choosing the correct type of firewall demands answering questions about what the firewall protects, how much money the business can pay, and how the infrastructure is laid out. The best firewall for one business may not be appropriate for another.

What types of traffic inspections are required?

Some applications may require that entire packet contents be monitored, whereas others may be fine with simply sorting packets based on source/destination addresses and ports. Because many firewall implementations combine features from many types of firewalls, choosing a type of firewall is rarely as straightforward as finding one that cleanly falls into any particular category.

How do firewalls work?

Firewalls examine packets for malicious code or attack vectors that have previously been identified as known threats. If a data packet is flagged as potentially dangerous, the firewall prevents it from entering the network or reaching your computer.

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