WatchGuard Firewalls: How Do They Work?

How do firewalls work? Well, they’re a little bit like the drawbridge to a castle, with a guard on patrol – but much smarter! Find out more about them.

WatchGuard Firewalls: How Do They Work?

At deeserve, we use WatchGuard firewalls in on-site hardware installations – including the flagship Firebox appliances – for their simplicity, performance and reliability. WatchGuard is the last word in network security hardware, and we believe that our customers deserve that kind of peace of mind.

But if you don’t know much about IT, you might be wondering… What is a firewall? And why’s it even called that, when it’s nothing to do with fire?

So, let’s give you a quick, simple introduction to firewalls – including why they’re named after a construction term, and how they work.

An Introduction to Firewalls

Okay – so what is a firewall?

In IT security, a firewall acts a little bit like the drawbridge to a castle, with a guard on patrol. The guard has a very strict set of rules about what’s allowed in through the castle gates. They’re constantly monitoring the flow of traffic in and out of the gate, and if anything that breaks the rules approaches – the gate gets closed, and the drawbridge goes up, so the rule-breaker in question can’t pass.

But firewalls are rarely applied with such brute force – although a total shutdown in high-security applications is possible.

In practice, firewalls are much smarter. In a computer network with a firewall, the data going in and out (over the internet or circulating within a company network) is constantly monitored. The rules on what can and can’t get through can be set to apply only to certain pieces of data – like anything that might be harmful, or malicious active attacks. This means that work can go on unaffected, while the firewall keeps the bad stuff out.

Firewalls can block unauthorised access, malicious software, and help prevent the sharing of insider information.

While firewall software can do this too, firewall hardware is accepted as the gold standard, mainly because it’s harder to get around. It also devotes 100% of its resources to monitoring and filtering, able to inspect data, reroute a connection or fully shut down access, based on the rules it’s given.

How do firewalls work?

There are a few ways to configure a firewall, which will ultimately define how it will work for your organisation.

One is a closed firewall – also called default deny firewalls – which is the most brute force approach, and often the most secure. In this setup, only authorised external networks can access the local network. This means any new networks must have explicit permission to get access.


This is super secure, but it can be a huge pain when you have large remote teams using many devices to work. If your company relies heavily on outside connection and data transfer, this might not be a suitable approach.

Other firewalls are classed as open firewalls, which allow all traffic through except for devices and networks that are specifically blocked. This is a more flexible solution – but it’s not as secure.

There’s a hybrid way, too – adding trusted networks, denying known bad ones, and applying strict rules to anything new that comes along. Finding a balance between security and accessibility for key people is the challenge, but WatchGuard’s hardware and configuration options make this far easier to manage than most platforms.

Okay – but why’s it called a firewall?!

Before the internet age, the word “firewall” was used in construction.

It was used to describe a wall that was built to stop the spread of fire to neighbouring buildings – which was rapidly being sought as a solution after the Great Fire of London and similar events in the USA. But in modern times and as regulations changed, we’d taken to calling the practice of isolating fires within buildings as “compartmentation”. This covers things like fire doors, fire curtains, and the all passive fire suppression tech built into buildings.

The term popped up again sometime during the late 1980s, in reference to network technology. And it makes sense – because just like a construction firewall is there to stop the spread of fire through buildings, an IT security firewall is intended to stop the spread of unauthorised access and malicious code through networks.

But the rise of the term in common language is probably thanks to the 1983 movie WarGames (starring a young Matthew Broderick, before he became Ferris Bueller).

The term was possibly used before this blockbuster film (it was nominated for three Oscars and won a BAFTA) but the huge exposure it got from the film is about the best evidence for it being the origin of the word.

And that’s why it’s called a firewall! If you want to learn about how WatchGuard firewalls can protect your business (and not just where the name comes from), get in touch below…

Protect Your Business, with deeserve.

We’re deeserve – a trusted partner to some of the largest organisations in the world. We choose WatchGuard firewalls as the gold standard for network protection. Protect your data and assets, with our expert team on hand, constantly monitoring and providing support.

Call us on 01509 808586 or send your message to to get started.

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