Difference Between SPI Firewall and Application Layer Firewall

If you’ve diverged a little deeper into the world of internet security than just discussing VPNs and how to protect your data online, then you have now come across firewalls and are confused about the types of firewalls and the levels of protection they can offer.

Although there are more than three types of firewalls out there, we are here to review and answer the query: what are the two main types of firewalls?

What is a Firewall?

More than 30 years after network firewalls first appeared on the security scene, the technology is still a vital part of any company’s arsenal when it comes to maintaining a secure network.

The firewall, a method for preventing harmful traffic from entering a network, has been in use for decades. However, as with any vital technology that has been in use for a long period of time, the firewall’s capabilities and implementation options have been improved.

The deployment of firewalls in private networks to block third-party access is a common practise.

Hardware and software-based network security systems (hardware/software-based) are used to monitor and manage traffic from the Internet to a private network. Protecting an organization’s computer network from unauthorized inbound or outbound access is the primary function of all types of firewalls.

How do Firewalls Work Exactly? 

Traditionally, server firewalls have been placed in the middle of a network connection to monitor all traffic travelling across it. In the process of doing so, they must determine which network protocol communication is legitimate and which is malicious.

The different types of firewalls use a set of established rules to filter out hazardous content from incoming traffic. It is impossible to foresee the intent of all content, but new technology has made it possible to apply recognised patterns in network data that have previously flagged similar attacks on other organisations.

For each packet that passes via a firewall, rules are applied that specify the conditions under which it can be safely forwarded to its intended receiver.

What are the Two Main Types of Firewalls and the Differences Between them? 

VeePN has done extensive research to bring you the differences between the most secure types of firewalls designed to protect your business’s sensitive and mission-critical information. 

1. Stateful Packet Inspection Firewall 

So what is SPI firewall and what benefits does it have for your company’s network protection? State-aware devices keep note of whether or not a packet belongs to an existing TCP or other network session.

While packet filtering or circuit monitoring alone provides higher security, this method takes a greater toll on network performance.

In addition to stateful inspection, multilayer inspection firewalls consider the flow of transactions across various protocol layers of the seven-layer OSI model.

Advantages of the SPI firewall: 

  • IP addresses and payloads are additionally checked for more extensive security measures during the entire session
  • High degree of control over what traffic is allowed in or out of the network does not necessitate opening several ports.
  • Provides comprehensive logging features

Disadvantages of the SPI firewall: 

  • Slows down network communications and consumes resources.
  • Other methods for firewalls are cheaper.
  • Inability to verify that traffic origins aren’t faked due to lack of authentication capabilities

A SPI firewall is beneficial to the majority of enterprises. In addition to connecting computers within the firewall with other assets, these devices also provide a link to resources outside the company’s walls. When protecting network devices from specific attacks like denial-of-service (DoS), they can be quite successful.

2. Application Layer Firewall 

This is another one in the category of what are the two main types of firewall. The sole way in and out of the network is through this device, which is technically a proxy but is also known as a proxy firewall.

Besides the service for which a packet is meant — as defined by the destination port — application-level gateways filter packets according to additional factors, such as the HTTP request string.

Even though application-layer gateways provide a high level of data security, they can significantly impact network speed and be difficult to operate.

Advantages of Application Layer Firewall 

  • In order to ensure that all communications between outside sources and devices behind the firewall are examined thoroughly, the proxy checks not only the address, port, and TCP header information but also the content itself.
  • Access to websites can be restricted, but only to certain pages, thanks to the fine-grained security restrictions provided by this feature.
  • ensures the privacy of the user

Disadvantages of the Application Layer Firewall 

  • Performance of a network can be impeded.
  • Inexpensive in comparison to some other firewall alternatives
  • To get the most out of the gateway, one must put in a lot of effort.
  • Some network protocols are incompatible.

Web application attacks are best mitigated by application-layer firewalls. In addition to blocking dangerous websites, firewalls can also prevent important information from leaking out of the network. In terms of communication delays, though, they can be problematic.


A private network’s security is protected by the most basic types of firewall configurations. Whatever server firewall you choose, make sure that it is configured correctly because even a small loophole can do more harm than having no firewall in the first place.

Create a secure network and put in place a firewall to keep your computer and network from being accessed by others.

Both types of firewalls have their advantages and disadvantages and are beneficial in protecting the connectivity of your servers and computers with the outside world. A firewall is an absolute necessity for any small, medium, or large enterprise in today’s world.

More and more businesses are now victims of cybercrime attacks and are losing funds and intellectual property to hackers. The goal is to combine the security measures like using an SPI firewall or any other kind of firewall, encouraging employees to use VPNs for research and browsing the internet, making sure you have a monthly session on browsing and internet usage etiquette, and keep reminding them of the importance of data integrity regularly. 

Taking all these safety measures together will ensure that your employees are not accidentally losing your data and also make sure that no one from an outside server can connect to your company servers. A myriad of security features is the only way to go and protect your data in 2021. 

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