Your firewall can see that traffic is leaving your network on port 443. It cannot see what is inside it. That gap is the reason next-generation firewalls exist.
Around 90% of web traffic is now encrypted, and the applications your team uses every day are almost all delivered over the same handful of ports. A rule set built around IP addresses and port numbers no longer describes how work happens. Add a hybrid workforce connecting from home, a branch office, or a phone on mobile data, and the old network perimeter stops being a useful place to draw a line.
Below we cover what a next-generation firewall does, how it differs from the firewall it replaced, and the criteria worth checking before you sign off on one.
What is a next-generation firewall (NGFW)?
A next-generation firewall is a firewall that inspects the contents of network traffic at the application layer, rather than making decisions purely on ports and IP addresses. Alongside stateful packet filtering, a NGFW adds deep packet inspection, application control, intrusion prevention, user identity awareness, and live threat intelligence in a single device.
The comparison makes it clearer. A traditional firewall reads packet headers. It works at OSI layers 2 to 4 and makes decisions based on source and destination IP address, port, and connection state. Traffic on port 443 is allowed, traffic on port 3389 is blocked, and that is roughly the extent of the judgement being made.
A NGFW keeps that stateful filtering and works up to layer 7, reading the payload as well as the header. That is what lets it tell the difference between a staff member using an approved SaaS platform and someone moving a database export out through the same encrypted connection on the same port.
The practical difference is visibility. Security teams rely on NGFWs to see which users, devices, and applications are on the network, and to apply threat protection wherever it is needed: at the branch, in the data centre, between internal network segments, in the cloud, and in operational technology environments.
Why traditional firewalls fell behind
Two shifts broke the old model.
The first is cloud adoption. When the applications your business depends on moved off your own servers, the traffic worth inspecting stopped passing through a single choke point. A firewall guarding the office internet connection sees very little of what an employee does in Microsoft 365 from a laptop at home.
The second is encryption. Modern threats including phishing payloads, ransomware droppers, and encrypted malware routinely pass through port-based firewalls because those firewalls never open the packet. TLS 1.3 makes this harder again, because it encrypts the server certificate and most of the handshake metadata, so a firewall has to actively terminate and re-establish the session to inspect it. That costs processing capacity, which is why performance under inspection matters so much when you compare products.
What to look for in a NGFW
The firewall protects corporate and customer data across both IT and OT environments, so the selection deserves proper scrutiny. Seven things are worth checking.
1. Integrated AI-powered security services
Security services powered by artificial intelligence complement traditional firewall capabilities by providing proactive threat detection and protection against evolving threats, including new AI-powered threats. Machine learning models analyse large volumes of traffic data to identify anomalous patterns that suggest malicious activity, and the firewall can adapt policy based on real-time analysis rather than waiting for a signature update. For a small internal IT team, this reduces workload and cuts the number of decisions a human has to make manually.
2. Threat protection performance
This measures how well a NGFW performs while running full threat protection, including firewalling, intrusion prevention, antivirus, and application control. It is critical that the device sustains high throughput with all of it turned on. Many vendors are ambiguous about how they represent their performance claims, and headline figures are often measured with inspection disabled. Read the documented claims carefully and check they reflect testing under load with threat protection fully engaged.
3. Single-pane-of-glass management
The management interface is where many security architects come unstuck. A well-designed interface counts for little if it only manages the firewall, because your team then has to toggle between dashboards to assess a vulnerability or respond to an incident. End-to-end visibility is only possible if the NGFW sits inside a broader security architecture and can share threat information with other network devices and receive intelligence automatically. It is also more efficient operationally, which shows up as less administrative time and lower training costs.
4. Fit with a broader security strategy
Distributed offices depending on redundant WAN links usually need more than a firewall. SD-WAN, zero-trust network access (ZTNA), and secure access service edge (SASE) all come into the picture. Plenty of vendors offer these as add-ons, which works but rarely works well. Look for a vendor with SD-WAN, SASE, and ZTNA capabilities built into the NGFW itself. Consolidating point products reduces overall investment and closes the gaps that appear between separate tools.
5. Price, performance, and running costs
Some vendors scale performance by increasing the size and price of the appliance, which sits awkwardly with the trend towards smaller technology footprints. Aim for the required performance in the most compact form factor available. A smaller NGFW reduces total cost of ownership, saves rack space, and draws less power. Factor maintenance and support into the TCO as well, because mature technology from a vendor with real research investment tends to mean smoother deployments and fewer support calls. On the hardware itself, check power redundancy and support for 40 GbE and 100 GbE interfaces so you are not replacing the device when your network capacity grows.
6. Purpose-built ASICs
Application-specific integrated circuits accelerate particular security functions such as packet processing, encryption, and decryption. Choosing a NGFW with well-designed ASICs is what allows it to handle high traffic volumes and inspect encrypted sessions in real time without adding latency, while consuming less energy than a general-purpose processor doing the same work. This is the single factor most often overlooked in a spec comparison.
7. Independent third-party validation
Network security moves quickly, but no business can afford an untested security product. Do not rely on vendor claims alone. Look for evaluation from a recognised testing house such as CyberRatings.org.
Your firewall as a sensor
The useful mental shift is this. A traditional firewall is a gate, and its job is to say yes or no at the boundary. A next-generation firewall is closer to a sensor that happens to be able to enforce policy. Its value comes as much from what it tells you about your network as from what it blocks.
That reframing changes how you evaluate one. A device that blocks well but reports into its own isolated dashboard leaves you with the same blind spots you started with. A device that feeds what it sees into the rest of your security stack, and acts automatically on what other tools send back, is worth more than its throughput numbers suggest.
Where to start if you are reviewing your current firewall
Begin with an inventory of what your current device can actually see. If it is not decrypting and inspecting TLS traffic, you have limited visibility into the majority of what crosses your network, and that is the first thing to establish.
Then work out where your edges are. Head office, each branch, remote staff, cloud workloads, and any operational technology all count. Consistent policy across all of them with minimal performance impact is the goal, and it is the main thing that separates a coherent architecture from a collection of appliances.
Given power and space constraints in most Australian office environments, favour compact solutions that can deploy at the edge or in the data centre without a rack full of hardware. Finally, confirm the NGFW integrates with your wider security architecture and can share threat intelligence with your other tools automatically.
Windstil provides cyber security consulting for Australian businesses, including Essential Eight compliance audits, ongoing threat management, and Virtual CISO support. If you are not sure what your current firewall can see, that is a sensible place to start.
