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Firewalls Explained: Different Types of Firewalls

Looking back at basic IT security, Firewalls were the beginning of protecting computers against viruses, malware, and other internet threats.

Fast forward to the present day and Firewalls are a major part of standard cybersecurity. However, there is still a bit of mystery surrounding what a Firewall does and what different types of protection there are. Aside from being preinstalled onto all Windows operating systems, do Firewalls keep you protected?

Here’s a quick overview of what a Firewall is, and the different types there are protecting networks today:

What is a Firewall?

The term ‘Firewall’ comes from a metaphor thought up from AT&T pioneer Steven M.Bellovin. He described a firewall as a ‘wall on fire’ that would prevent intruders like viruses, trojans, ransomware and other malicious things from coming into your network and infecting them.

How do they work?

A firewall is a system that filters incoming and outgoing network traffic. It really is as simple as that.

If some traffic is unusual or out of the ordinary, then the Firewall will block or freeze it accessing the network. Often prompting the user via a notification. The user can then decide whether to allow or continue to block the incoming program.

The different types of Firewalls:

So, we’ve established that Firewalls are good and do provide value to businesses – but what different types of Firewalls are there?

1. Packet Filtering Firewall

The first type of Firewall created for network security. This Firewall was designed to filter and inspect data packets entering the network based on an established set of rules. These rules are input by the system but can be added to or changed by the user. Potential variations could be allowing certain IP addresses, packet types or port numbers or potentially blocking them.

2. Circuit Level Firewall or Gateway

These are more detailed Firewalls, observing TCP (transmission control protocol) connections and sessions. They are in place is to ensure any external sessions your network encounters, are safe and legitimate ones. Again, alerting the user or blocking the potential danger.

3. Stateful Inspection Firewall

A combination of Packet filtering and circuit level Firewalls. These Firewalls monitor all active sessions or connections, giving them the most power in evaluating whether networks packets should be permitted or blocked.

4. Application-level gateways

This kind of Firewall is also known as a proxy Firewall. Where this combines the features of packet filtering firewalls with those of circuit level gateways. Meaning that they filter packets not only for the service for which they are used.

5. Next-gen firewalls

Finally, the most advanced and most recent development of Firewall is Next-gen Firewalls. A typical next-gen product combines packet inspection with stateful inspection. Some next-gen models also provide a variety of deep packet inspection.

Next steps?

Firewalls are encouraged by us as a basic level of protection. All genuine Windows operating systems come with Windows Defender, but we would always recommend have extra protection in the form of antivirus protection.

If after reading this and are worried about the internet security you currently have. Then please get in contact with us on 02920 887 362 or send us an email at

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