9 Firewall Types (With Tips for Choosing a Firewall)

Updated March 22, 2023

An IT team stares intently at a computer screen as one of the team members types on a keyboard.

Businesses and private individuals often have sensitive information on their devices that may require protection from malware, ransomware, distributed denial of service (DDoS) attacks, spam and other attacks.

Firewalls are essential to the security of a system because they can protect it from attacks that may compromise networks, services, software and sensitive data. Understanding how firewalls work and the different firewall types can help businesses and cybersecurity personnel better determine which type is best for their network.

In this article, we discuss what a firewall is, nine types of firewalls, how they differ from virtual private networks (VPNs) and tips for choosing the right type of firewall for your cybersecurity needs.

Related: Working in Cybersecurity: Definition, Careers and Skills

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What is a firewall?

A firewall is a security solution that monitors incoming and outgoing network traffic to prevent unauthorized access from hackers or other bad actors. It filters the network's traffic by separating different network nodes to determine which adheres to various access control policy rules the firewall administrator sets.

Network nodes are points of connection between networks. Firewalls can filter external traffic sources, internal traffic and specific applications to determine which users or applications may access a network. This additional security can protect private or sensitive information from breaches by unauthorized sources while also filtering out malicious traffic.

Related: What Is a Network Firewall? (Plus Benefits, Types and Steps)

9 important firewall types

Here are a few important firewall types for you to review:

1. Software firewall

You install a software firewall as an application on individual devices, and it has custom rules that help it filter network traffic. Software firewalls can allow access to one application or feature while blocking others. This type of firewall can be beneficial if you want to protect a particular device against cyber threats, and it requires individual configuration and management. Not all devices are compatible with a single software firewall, so additional firewalls may be necessary. 

Related: 28 Cybersecurity Tools You Can Use at Work (Plus Key Features)

2. Hardware firewall

A hardware firewall is a physical device that uses its computing power to filter network access. Firewalls can protect various devices on the same network, making them easier for large networks. Hardware firewalls typically protect the devices by filtering network traffic between different parts of a network. They don't offer protection from insider attacks, which include any unauthorized access or misuse of a network by internal employees or contractors. 

Related: 8 Hardware and Networking Interview Questions With Answers

3. Packet filtering firewall

A packet filtering firewall checks data packets for their source Internet Protocol (IP) address and the packet's destination IP to compare to the network administrator's predetermined set of rules. These rules include attributes such as source and destination IP addresses, port numbers and protocols.

Packet filtering firewalls monitor each packet independently without tracking the established connection and typically have limited capacity. This means they can't detect or prevent application-layer attacks like malware or buffer overflow attacks. Cybersecurity personnel typically use this firewall type to protect networks from malware and harmful applications. 

Read more: What Is Packet Filtering? (Benefits and Types)

4. Circuit-level gateway

A circuit-level gateway is a firewall that monitors Transmission Control Protocol (TCP) connections and active sessions. The network administrator establishes preset rules that guide these connections, and circuit-level gateways perform checks on them that function similarly to packet-filtering checks.

These firewalls don't analyze the contents of the data packet associated with the TCP, so they may not offer consistent protection against more sophisticated types of malware. A circuit-level gateway can be a cost-effective security solution when used with other types of firewalls. 

Related: Computer Networking Basics: Everything You Need To Know

5. Proxy service application firewall

A proxy service firewall uses a proxy device to verify requests from external users at the application level by inspecting the contents of their data packet and comparing them to a set of rules defined by the network administrator. Based on this analysis, the firewall then admits or denies access to the network.

When accessing external web pages, these firewalls can also hide internal users' identities and IP addresses. This process can be time-consuming because of its thoroughness, but it can protect sensitive information by preventing direct contact between external clients and the internal server.

Related: 111 Cybersecurity Interview Questions (With Sample Answers)

6. Cloud firewall

A cloud firewall is a security product that operates on the cloud and mitigates undesired access to private networks. Like a traditional firewall, cloud firewalls filter out potentially malicious network traffic, but they differ in that they operate entirely in the cloud.

These firewalls can be software-as-a-service (SaaS), and users can subscribe to them to use their security. They typically protect online applications hosted in the cloud from unauthorized access using multifactor authentication and encryption.

Related: What Is a Virtual Cloud Network? (Plus How They Work)

7. Stateful inspection firewall

A stateful inspection firewall is an advanced version of a circuit-level firewall that also verifies and tracks established connections to provide more comprehensive security. These firewalls create a table that records the source IP, destination IP, source port and destination port.

They drop connections they can't verify, eliminating suspicious activity. The firewall then sorts through the connections using the filters established by the network administrator. Additionally, the firewall creates its own rules that can filter the contents of the data packets, making them more accurate. It can also monitor all active TCP and User Datagram Protocol (UDP) values.

Related: What Is System Hardening? (Definition and How It Works)

8. Next-Generation firewall (NGFW)

A next-generation firewall (NGFW) combines traditional firewall technologies with newer filtering functions, like deep packet inspection (DPI) and intrusion prevention systems (IPS). Many NGFWs have traditional firewall functions like packet filtering or stateful inspection and merge them with newer technologies. The goal of the newer technologies is to improve the filtering of network packets by including more layers in the Open Systems Interconnection (OSI) model in its filtration.

9. Network address translation (NAT) firewall

A network address translation (NAT) firewall matches a local private address to a public address to transfer information to ensure local network security. Changing the address from the device's private address to a router's public address helps the device communicate with external networks by providing a public location for the network to send its information.

Organizations that use multiple devices but want a single IP address use NAT firewalls to translate the unique addresses onto public addresses. This type of firewall can block unwanted or malicious data and prevent hackers from accessing local networks.

Firewalls vs. VPNs

A virtual private network (VPN) is a network that provides online privacy and instant connection by creating a private network from a public connection. It protects your online identity by concealing your data packets and IP address, offering increased anonymity.

While firewalls protect an entire system from intrusion, VPNs protect a single user's identity. Companies may use both firewalls and VPNs to share files on a secure network and increase privacy. They typically use firewalls to block attacks and VPNs to encrypt their data. 

Related: Pros and Cons of 6 Virtual Private Network (VPN) Protocols

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Tips for choosing the right firewall 

Many cybersecurity specialists and analysts use multiple firewalls to segregate networks with varying security needs. Using firewalls can provide a high level of protection from both inside and outside threats to a network. Here are a few helpful tips for choosing the right firewall type:

Consider your preferences 

Different firewalls typically allow varying degrees of accessibility. More traditional firewalls may offer more limited accessibility. Choosing a nontraditional or NGFW firewall can help you apply policies to certain end-users, allowing access to people who require a specific application for their job and limiting access to people who don't commonly use the application. These firewalls can also limit access to different parts of applications, offering additional security.

Decide on the security infrastructure 

Different firewalls often have varying security infrastructure components. Many modern firewalls contain anti-virus protection, spam filtering tools, application filtering and deep packet inspection. Consider the features you need. More robust firewalls typically offer a wider variety of security components. Spend time researching the different firewall types to learn what they offer.

Think about the cost

Modern firewalls may be more expensive, but they can also offer a broader range of components and useful features. It's also important to consider the potential cost of a malicious attack or the replacement cost of hardware or software resulting from such an attack when determining whether a firewall is worth purchasing. Review your cybersecurity budget and research the costs of different firewalls. You may also consider trialing different firewalls before making a purchase.

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