A firewall controls which network traffic can enter, leave or move between your systems. It blocks traffic that breaks its rules and allows approved connections through.
For an Australian SMB, simply owning a firewall is not enough. It must cover the right traffic paths, stay current, and have clear ownership of its rules and alerts.
The challenge is that the biggest firewall gaps are often hard to spot. An outdated rule, exposed admin page or ignored alert can leave a door open long after everyone assumes the network is protected.
What Is a Firewall?
A firewall is a security control that allows or blocks network traffic according to defined rules.
It can sit between your office and the internet, between internal network segments, around cloud workloads, in front of a web application or on an individual computer.
That makes a firewall one part of cybersecurity, alongside identity, endpoint, email, application and data controls.
Furthermore, depending on its features and configuration, a firewall can block:
- Unsolicited inbound connections
- Disallowed ports, protocols, applications or destinations
- Known malicious addresses, domains or websites
- Suspicious requests or exploit patterns
- Unapproved outbound traffic or movement between network segments.
What firewall actually stops depends on what it can see and how well its rules are maintained. Let’s say, one broad exception or an unpatched firewall can leave a path open even when the control is switched on.
How a Firewall Works
A firewall works by matching network traffic against rules and inspecting enough context to decide what should happen.
Two things shape every decision: the rules define permitted traffic, while the inspection method determines what the firewall can see. The basic flow looks like this:
| Step | What the firewall does |
|---|---|
| Identify | Reads details such as the source, destination, port and protocol |
| Inspect | Checks the connection state, application or content when supported |
| Match | Finds the rule that applies to the traffic |
| Act | Allows, rejects or drops the connection |
| Record | Logs the event or creates an alert when configured to do so |
Firewall Rules
Firewall rules define which traffic may cross a boundary and what happens when it matches.
In practice, a rule is only useful when your team can explain why it exists, who approved it and when it should be reviewed. A workable rule should record:
- The source and destination
- The service, port, protocol, application or user
- Whether to allow, block, log or alert
- The business purpose and approver
- The owner and review or expiry date
Those details matter most when access is temporary. Supplier access and testing exceptions need expiry dates so they do not quietly become permanent.
Start from a default-deny position, then allow only the traffic a legitimate service needs. This aligns with Australia’s ASD-led security guidance for edge devices, which recommends blocking traffic unless a rule expressly permits it.
Traffic Inspection Methods
Traffic inspection methods range from simple header checks to connection tracking and application-content analysis.
The more context a firewall can inspect, the more precisely it can apply its rules. That added visibility, however, also requires more processing power and careful configuration.
| Method | What it checks | Practical use |
|---|---|---|
| Packet filtering | Addresses, ports and protocols | Fast control of predictable traffic |
| Stateful inspection | Packet details and connection state | Separates expected response traffic from unrelated packets |
| Application-layer inspection | Protocol commands and application behaviour | Applies more precise rules to services and applications |
| Deep packet inspection | Headers and available payload content | Detects some threats inside permitted traffic |
| URL and reputation filtering | Destinations against policy or threat intelligence | Blocks prohibited categories or known risky destinations |
The table shows the trade-off: deeper inspection gives your team stronger context, while simpler methods suit known, predictable traffic.
Encrypted traffic adds another consideration because it can hide information from the firewall.
TLS inspection can restore some visibility, but your team needs to weigh the certificate, privacy, compatibility and performance impact before enabling it.
Types of Firewalls
The main six firewall types differ in what they inspect and what they protect. The six types below cover the most common decisions for network, application and cloud security.
| Firewall type | Main strength | Common fit |
|---|---|---|
| Packet filtering | Simple header-based control | Tightly defined network traffic |
| Stateful inspection | Connection-aware decisions | Office, branch and internal networks |
| Proxy | Application-level intermediation | Closely controlled services |
| Next-generation firewall | Application visibility and threat prevention | Networks needing deeper inspection |
| Web application firewall | HTTP and HTTPS request filtering | Public websites, portals and APIs |
| Cloud firewall | Policy enforcement around cloud resources | Cloud and hybrid environments |
Packet Filtering Firewalls
Packet filtering firewalls allow or block packets by checking addresses, ports and protocols.
They are fast and suit narrow, predictable traffic, but they do not track the full conversation or inspect the application payload.
Stateful Inspection Firewalls
Stateful inspection firewalls track active connections and use that context when deciding whether a packet belongs.
This makes them a practical foundation for network firewalls, provided the rules, software and administration stay current.
Proxy Firewalls
Proxy firewalls sit between a client and its destination rather than allowing a direct connection.
Their application-level control can protect internal systems, although it may add latency, compatibility work and administration.
Next-Generation Firewalls
A next-generation firewall combines stateful inspection with features such as application control, intrusion prevention, deep packet inspection, URL filtering and threat intelligence.
That’s why, before buying, compare throughput with those services enabled and confirm who will tune policies and alerts after deployment.
Web Application Firewalls
A web application firewall, or WAF, filters HTTP and HTTPS requests sent to a web application or API.
As an application firewall for HTTP applications, WAF supports secure coding, patching and web application penetration testing rather than replacing them.
Cloud Firewalls
Cloud firewalls apply traffic policy around cloud networks, workloads and services. They may be cloud-native controls, virtual firewalls or managed services.
Check that every account, region and environment follows consistent rules and sends logs to one visible location.
Firewall Deployment Options
Hardware appliances, host-based software and firewall-as-a-service are the three main deployment options that determine where firewall protection sits and which traffic it can inspect.
The sections below explain where each option fits and when a mix of them may suit your environment better.
Hardware Appliances
Hardware firewall appliances protect many devices from a network boundary, such as an office, branch or data centre.
They suit central routeing, segmentation and VPN access, but they need secure administration, supported firmware, configuration backups and a failover plan where downtime matters.
Host-Based Software
Host-based firewall software controls traffic to and from one workstation, server or virtual machine.
It keeps protecting laptops away from the office and can limit movement inside a network, provided your team manages settings and exceptions centrally. Internal penetration testing shows whether those limits hold once an attacker already has access to a device on the network.
Firewall as a Service
Firewall as a Service, or FWaaS, delivers firewall policy through a provider-operated cloud platform.
It can apply consistent rules to remote users, branches and cloud resources, but buyers should still check traffic routing, latency, identity integration, log access, service availability and exit options.
Firewall Compared With Antivirus and VPN
Your firewall controls traffic, endpoint protection handles malicious activity on devices, and a VPN encrypts a connection in transit. That’s why we can say a firewall, antivirus software and a VPN solve different security problems.
| Control | Main job | It does not replace |
|---|---|---|
| Firewall | Allows or blocks network traffic | Endpoint, identity or application security |
| Antivirus or endpoint protection | Detects and responds to malicious files or behaviour | Network traffic control |
| VPN | Encrypts traffic between trusted points | Firewall inspection or malware detection |
Firewall and Antivirus
A firewall controls connections, while antivirus or endpoint protection examines files, processes and behaviour on a device.
You can use both where those risks apply because a firewall cannot remove malware that arrived through an allowed channel or was introduced locally.
Firewall and VPN
A firewall decides which connections are allowed, while a VPN creates an encrypted tunnel between users, devices or networks.
Secure remote access normally needs both, together with MFA, password management, endpoint protection, restricted access and useful logging.
What a Firewall Does Not Protect Against
A firewall cannot stop a cyberattack that uses an approved path, a trusted account or a weakness outside the traffic it inspects.
That does not make the firewall less useful; it shows where its protection ends and where other controls need to take over:
- Stolen credentials: An attacker can sign in through an allowed service with a legitimate username and password. Use MFA, access controls and login monitoring to catch or limit that access.
- Social engineering: A person may be manipulated by email, message or phone before the firewall has anything to block. Back staff awareness with payment and identity checks.
- Malware on permitted traffic: A malicious file can arrive through email, cloud storage or encrypted web traffic that the firewall allows. Endpoint and email protection help inspect and contain it.
- Unpatched vulnerabilities: A firewall, VPN or application can still have an exploitable flaw. Keep systems patched and use vulnerability management to find weaknesses early.
- Cloud or application misconfiguration: The weakness may sit outside the network path the firewall inspects. Secure configuration, access reviews and penetration testing help close those gaps.
- Human error, insider action or device loss: Legitimate access or physical possession can bypass network rules. Least privilege, encryption and data loss prevention controls reduce the impact.
Because these risks can sit on allowed paths or outside network inspection, a cyberattack can still succeed while a firewall is active.
A data breach can also begin without an external intrusion. So, treat your firewall as one layer within a wider set of identity, endpoint, data, recovery and response controls, which a cybersecurity strategy sets out and prioritises.
Firewalls in Australian Compliance Requirements
Firewalls can support cyber security compliance, tenders and insurance evidence, but they do not prove overall security on their own.
For Australian SMBs, focus on three questions: what SMB1001 expects, what the Essential Eight does not cover, and what firewall evidence an insurer may ask to see. Let’s break it apart.
SMB1001 Firewall Controls
In SMB1001 Bronze, firewall protection is treated as a foundational control for reducing basic network risk.
For reference, Dynamic Standards International lists firewalls and antivirus software as basic controls in its SMB1001 Level 1 overview.
In practice, the firewall needs to be securely configured and actively managed, rather than simply present on the network.
To confirm that the control is operating as intended, confirm the firewall is:
- Deployed at relevant boundaries and enabled on supported endpoints
- Configured to allow only required access
- Protected from public administrative access
- Running supported, current software or firmware
- Assigned to an owner responsible for reviews, changes and evidence
Together, these checks show that the firewall is maintained, rather than merely installed.
They also form part of the wider SMB1001 control set, where the SMB1001 Bronze, Silver and Gold levels add further safeguards and evidence helps demonstrate that each one is in place and being managed.
That same evidence gives procurement teams a clearer view of your security position when a customer asks for security information or a tender requires it.
The Essential Eight Gap
Firewalls sit outside the Essential Eight, so reaching an Essential Eight maturity target alone does not show how your network is protected.
ASD addresses segmentation, restricted traffic flows and firewall-related logging separately in its guidelines for networking.
That separation matters when a customer or tender asks about both areas. Your Essential Eight maturity shows how you meet the eight strategies, while your firewall evidence shows how network access, rules and logging are managed.
A cybersecurity compliance map can bring those answers together by linking each requirement from Essential Eight and SMB1001 to the relevant control, its owner and the evidence you can provide.
Cyber Insurance Questions About Firewalls
Cyber insurers may ask whether business-grade firewalls protect your external gateways. That question usually sits within a wider review of how well your business maintains its security controls and can evidence them.
Some cyber insurance proposals may ask you to confirm firewall protection if you cannot confirm Essential Eight Maturity Level One.
If yours does, your answer should be backed by records that show what the firewall protects, how it is configured and who reviews it:
- Firewall product, support status and protected locations
- Network diagram and internet-facing services
- Rule and configuration standards
- Patch, firmware and vulnerability records
- Recent rule reviews, approved changes and alert ownership
Having this evidence makes renewal and application questions easier to answer, but it does not guarantee cover, favourable terms or claim acceptance. Confirm the specific requirements in your own proposal with your broker or insurer.
What Australian SMBs Weigh When Choosing a Firewall
Australian SMBs usually choose a firewall around three practical factors: the traffic it must cover, the team that will maintain it, and the visibility needed from its logs. These factors shape the three decisions below:
| Decision area | Question to answer |
|---|---|
| Network size and remote access | Which users, sites, devices, cloud resources and public services need coverage? |
| Rule maintenance and change control | Who approves, tests, records, reviews and removes access? |
| Logging and alert visibility | Which events matter, where do the logs go and who acts? |
As your reference, the ASD’s Small Business Cyber Security Guide supports the same approach by recommending that SMBs minimise internet-exposed services, secure routers and consider mature cloud services with built-in security.
Network Size and Remote Access
Network size and remote access determine how much traffic your firewall must process and where it needs to apply protection.
You can start by mapping the real traffic paths it needs to cover, then confirm it can inspect them without becoming a bottleneck:
- Internet bandwidth and inspected throughput
- Office, branch, home and mobile working patterns
- Concurrent remote-access users
- Public websites, APIs and administration services
- Guest, IoT, server and sensitive network segments
- Cloud platforms and direct cloud connections
- Failover and recovery requirements
These factors matter more than employee numbers alone. For example, a small SaaS team with public applications and heavy cloud traffic may need more capacity and more complex policy than a larger office using standard cloud software.
Rule Maintenance and Change Control
Rule maintenance and change control keep firewall access from expanding unchecked as your systems, suppliers and remote-access needs change.
Choose a firewall your team can maintain, then make each rule part of a routine that:
- Starts with default deny and grants the least access needed
- Names the purpose, owner, approver and affected service
- Gives temporary rules an expiry date
- Tests changes and keeps a rollback path
- Reviews rules after major changes and on a set schedule
- Removes access for retired systems, suppliers and users
This routine gives your team a clear record of why access exists, who approved it and when it should be removed.
If your team does not have the capacity to run that cycle, ongoing firewall administration can form part of a managed security service.
Logging and Alert Visibility
Logging and alert visibility give your team the context to act when something changes or looks wrong. Choose a firewall that provides useful signals, then confirm it can:
- Record useful allowed, denied and administrator activity
- Send logs to a central platform
- Alert on high-risk events and ruleset violations
- Keep consistent timestamps for investigation
- Retain evidence for operational, customer or insurance needs
- Route alerts to named contacts with defined actions
The main idea is to turn firewall activity into timely action, rather than an archive no one reviews.
Alerts matter because they can help identify suspicious traffic, failures and configuration changes while your team can still respond. Logs and alerts show what is happening on the network.
A vulnerability assessment can then identify exposed or unpatched firewalls, VPNs and management interfaces, while a configuration review checks whether the rules themselves still make sense. External penetration testing goes further by attempting to reach those internet-facing services the way an attacker would.
Protect Your Network With RedScale
Firewall gaps often surface when a client, tender process or insurer asks your team to prove what is protected, who owns it and whether rules are reviewed.
If those records are missing, your team may be chasing rule exports and network diagrams while a project is pending or a renewal deadline is approaching.
Stale access, unsupported firmware and unowned alerts are harder to find and fix under that pressure.
That is why RedScale’s SMB1001 certification support connects firewall review and remediation with the ownership, records and supporting evidence needed for SMB1001 preparation, supplier onboarding and customer security reviews.
Our service gives your team a practical way to explain how the control is managed when a client, insurer or assessor asks.
Book a discussion with RedScale about your SMB1001 readiness, and get a clear view of where your firewall gaps sit.
