The 5 Main Types Of Firewalls Explained

The internet contains harmful elements that can compromise your network and misuse your data. It’s crucial to protect yourself by installing a firewall that’s appropriate for your network. Unfortunately, many people are unaware of what a firewall is and how it can safeguard their network from threats.

Well, to give you an idea, a firewall acts as a first line of defense against malicious threats and attacks present on the internet that can misuse your network or your data. In this article, we will be discussing firewalls in detail including, what they are, how they can help different networks, and how you can take advantage of them.

What are Firewalls?

A firewall is a security system for networks that monitors and controls incoming and outgoing network traffic. It manages data packets containing the sender and recipient’s IP addresses and port numbers.

Firewalls manage these data packages by either allowing or preventing them based on a predefined set of security rules. The purpose of a firewall is to prevent harmful traffic, such as viruses, prevent hackers from entering your internal network by creating a barrier between it and external sources like the Internet.

How Do Firewalls Work to Prevent Network Threats

Imagine your network as your personal property. Would you permit strangers to enter, explore or take things from it? Firewalls aid in monitoring the traffic that visits your network and allows trusted sources to pass while blocking or reporting the harmful ones. They protect the entry point of a network, known as ports or choke points, where external devices exchange information.

Refer to our article if you want to check for the blocked choke points or ports: How to Check if Windows Firewall is Blocking Ports.

Technically, the purpose of a firewall is to check each incoming and outgoing data packet according to a set of rules. If the packet matches one of the rules, it is permitted to continue to its intended destination. If a rule exists to block a certain type of packet, or a packet containing certain information or metadata, the firewall will block or report it.

Firewall rules are configured as Access Control Lists (ACLs), which are lists of permissions that allow or deny traffic. An ACL includes an action like allow, deny, or reject, along with conditions or parameters that must be met for the action to be applied. For security reasons, firewalls typically use a “deny by default” policy, which means that any traffic that doesn’t meet the criteria in the firewall rules will be denied automatically.

Note: Make sure that the settings of your Windows Firewalls aren’t messed up. In case you find anything usual, reset the settings.

Different Types of Firewalls and Their Frameworks

Firewalls come in different shapes and sizes. By that, we mean that a firewall can be in the form of software or hardware. You may have seen huge data centers (at least in the movies) that have huge racks of servers installed. Usually, there is a firewall installed somewhere within those racks. This is a firewall in its hardware form. Some of the famous brands with hardware firewalls include Cisco, Juniper, Barracuda, and many more.

There are also many firewall software available today, like Sophos, FortiGate, pFSense, and Palo Alto (to name a few). These can be installed on servers and configured as firewalls to monitor, scan and filter incoming and outgoing traffic.

The software category also covers some cloud-based firewalls, like AWS Network Firewall. Software firewalls are designed to protect an individual computer or device from malicious activity, while cloud-based firewalls are hosted online and manage traffic flows between different networks.

On the other hand, Cloud-based firewalls offer extra security benefits like DDoS protection and threat intelligence insights. They can also monitor user activities to detect suspicious behavior on your network.

In addition to these types of firewalls, firewalls are also categorized through their framework. By “framework”, we mean their operation mode and behavior.

In this article, we will discuss the different types of firewalls and their role in protecting our networks against threats and hackers.

Packet Filtering Firewalls

Packet-filtering firewalls are the oldest type of firewall that create checkpoints at individual routers or switches. They check data packets attempting to enter the network without inspecting their contents. The purpose of packet-filtering firewalls is to prevent any suspicious information from entering the network without affecting its performance.

How Packet Filtering Firewalls Work

A packet filtering firewall performs its work by a process canned “Packet Switching.” The process of packet switching involves breaking data into smaller packets as it travels through a network, and is transmitted via different paths. These packets are then rearranged by the firewall before reaching their destinations.

Each packet consists of two components: Packet headers, which include IP and other routing information, and a payload, which contains the user data.

Who Can Use Packet Filtering Firewalls

Anyone, including individuals, small businesses, and even Internet Service Providers (ISPs), can use packet filtering firewalls to protect their computer networks from unauthorized access or malicious attacks.

However, since such firewalls cannot handle large amounts of packets, large enterprises shouldn’t use this firewall framework.

Utilizing Packet Filtering Firewalls

A packet filtering firewall can be used in two ways:

• By Blocking Specific IP Addresses:

  To prevent potential attacks, organizations can configure their firewall to block incoming packets from certain IP addresses that are known to be sources of malicious traffic.

• Restricting access to specific services:

  This type of firewall can be set up to permit incoming packets that are intended for particular services like web or mail servers. Doing this only permits genuine traffic to pass and aids in preventing denial-of-service attacks.

Stateful Inspection Firewalls

Stateful inspection firewalls are a type of firewall that functions at the transport layer of the Open Systems Interconnection (OSI) model. It scrutinizes all incoming and outgoing packets in conjunction with the connection state.

As a result, the firewall can keep track of the connection’s current state and oversee its progress from start to finish.

How Stateful Inspection Firewalls Work

Stateful inspection firewalls keep a detailed record of all network connections passing through them, known as a “State Table.” The table includes information like source and destination IP addresses, ports, sequence numbers, and acknowledgment numbers. The firewall uses this information to analyze incoming and outgoing traffic and decide whether to allow or block it based on security policies.

The firewall checks incoming packets against a set of rules to decide if they should be allowed or not based on various factors such as IP address, port number, protocol, and application type. It examines the contents of a data packet and then compares them against data in the packets that have previously passed through the firewall. 

If a packet meets the criteria, the firewall then looks at its state table to determine whether it’s part of an already established connection. In case the packet is not valid or belongs to an unrecognized connection, the firewall will either ignore it or subject it to increased scrutiny using the configured rules.

Who Can Use Stateful Inspection Firewalls

Medium to large organizations can benefit from using stateful inspection firewalls as they offer a comprehensive security solution that can handle high traffic volumes. Businesses like financial institutions, hospitals, and government agencies that require strong network protection can particularly take advantage of stateful inspection firewalls.

Utilizing Stateful Inspection Firewalls

As the name of these types of firewalls suggest, there is only one way to use these firewalls: By determining the state of the network connections.

A firewall can monitor the status of network connections between hosts and decide whether to allow or block traffic based on the current status of the connection. This means that if there’s an ongoing connection between two hosts, the firewall can be set up to permit traffic between them until the connection ends or expires.

Proxy Firewalls

This firewall type examines network traffic at the application level. They provide advanced security features by analyzing both the data as well as the headers of incoming traffic at the highest level of the OSI model.

A proxy firewall is considered one of the safest firewall types, as the firewall itself acts like a proxy. No outgoing traffic is sent directly from the inside network onto the internet. Instead, it is sent from the proxy firewall. The same is true when an inbound data packet is entering the network through the proxy firewall.

How Proxy Firewalls Work

They function as a go-between for clients and servers and scrutinize every request before sending it to its intended target. This allows the firewall to validate authorized traffic and discourage harmful packets from passing through. Proxy firewalls are extensively used by businesses to protect their web applications against cyber threats.

Proxy firewalls are also considered a suitable option for scenarios requiring network anonymity.

Who Can Use Proxy Firewalls

Proxy firewalls are a great solution for businesses that manage sensitive information, for example, financial companies, and healthcare providers.

Proxy firewalls are also frequently used by remote workers who need to access the company’s network from outside of the office. They offer extra protection against cyber-attacks which may target employees who work remotely.

Utilizing Proxy Firewalls

Proxy firewalls are used through web filtering. To ensure productivity and efficient use of bandwidth, many organizations control the websites that employees can access.

Circuit-Level Gateways

Circuit-level gateways are another type of firewall that operates at the session layer of the OSI model and monitors the TCP handshakes of local and remote hosts. They are a simple type of firewall that can quickly allow or block traffic without using many resources.

However, because they do not inspect the packets, they may allow requests containing malware to enter if a proper TCP handshake occurs.

How Circuit-Level Gateways Work

A firewall that operates at the circuit level doesn’t examine the actual content of data transmissions, which makes it prone to malicious attacks. However, it can quickly verify Transmission Control Protocol (TCP) connections from the sessions layer of the OSI model with minimal resources and block unwanted network connections.

That’s why most network security solutions, including software firewalls, have circuit-level gateways. These gateways create virtual connections for each session and can also conceal a user’s IP address.

Who Can Use Circuit-Level Gateways

Circuit application firewalls are beneficial for organizations that heavily use web-based applications. They can also be used by businesses that manage sensitive data, such as Personal Identification Information (PII) and financial information.

Utilizing Circuit-Level Gateways

Cirtcuit-level gateways are usually implemented in a multilayered approach. One way to enhance network security is by using circuit-level gateway firewalls in addition to other measures like Intrusion Detection Systems (IDS) and Virtual Private Networks (VPNs).

By implementing this multi-layered approach, it becomes harder for hackers to breach the network while having the ability to instantly block certain traffic sessions.

Next-Generation Firewalls (NGFW)

NGFWs, also known as Next-Generation Firewalls, are the most advanced type of firewall available today. They can thoroughly examine every packet, including the contents, and can detect and block complex threats such as malware, viruses, and intrusion attempts.

NGFWs come equipped with features such as SSL decryption, URL filtering, and advanced threat protection, making them the most effective type of firewall available.

How Next-Generation Firewalls Work

NGFWs are advanced firewalls that provide a comprehensive network security solution. These gateways can inspect and filter traffic at the application layer, and use deep packet inspection to identify and categorize data packets entering or leaving a network.

Who Can Use NGFWs

NGFWs can be costly and complex to handle. Small businesses may lack the necessary funds to invest in them, while large corporations may have to hire IT professionals specifically for the management of their NGFW systems.

That said, NGFWs are for those who take their cyber security seriously and want to protect their data, servers, and devices at all costs.

Utilizing Next-Generation Firewalls

NGFWs are operated through compliance policies. NGFWs can aid organizations in implementing compliance policies by utilizing traffic monitoring for specific keywords, protocols, or data types. This helps to maintain the confidentiality of sensitive data and to guarantee compliance with regulatory standards.

Conclusion

Different types of firewalls vary in their functionalities. Basic firewalls only verify sessions and packets without inspecting the content. Gateway firewalls establish virtual connections and restrict access to private IP addresses.

Stateful firewalls maintain a state table using TCP handshakes to track connections. While an NGFW may seem the most secure option, it might only be appropriate in some situations.

It would be best if you chose something depending upon your system’s level and something compatible with your budget. You may opt for a software firewall if your network isn’t very vast. In fact, if your computer does not have any sensitive information, you may as well be using the Windows Defender Firewall that comes preinstalled in the Windows OS.

However, if you are a small or medium-sized company, then you may want to opt for a hardware firewall, or software if you have a server to spare.

If you are wondering what type of firewall you should choose based on its framework and mode of operating, then you can find a complete guide to it above in this post.