What is a Virtual Firewall?

How is a Firewall Made Virtual?

Traditional networking appliances require dedicated hardware for each network function: the firewall is one of the most well-established pieces of hardware within the security stack. In this setup, incoming traffic is routed to the firewall that is plugged into the router, where it’s analyzed, before being forwarded to the internal network’s own switches. Sometimes, hardware firewall apps can be built into the router itself. The onboard memory then executes the security policies and routes traffic on to the internal networks. Usage trends are stored temporarily onboard; these can be extracted and analyzed by other security tools like security information and event management (SIEM).

The firewall analyzes every packet of data that is sent to the protected network, filtering traffic according to its criteria. This includes protocol type, source and destination IP addresses, port numbers, and previous behavior. If a packet does not comply with these rules, the firewall prevents it from passing through. In physical networks, these rules are uploaded to the physical appliance. However, continuing to rely on a hardware firewall can lock admin teams into expensive upgrade cycles as a business – and its network traffic – grows.

Separating  compute power from a physical machine has been the defining process of the last decade’s worth of cloud transformation. Network Function Virtualization (NFV) allows firewalls to be virtualized through a type of software called a hypervisor. This segments a physical machine into multiple virtual machines – each of which can run independently. This then allows a firewall to be purchased and deployed as software: traffic on-route to the network is routed via this cloud-based, virtual firewall. An organization then maintains the  virtual firewall, changing rules and viewing ongoing activity through a visual dashboard.

Virtual vs Physical Firewall Use Cases

Since virtual firewalls are so different from their hardware-based counterparts, their ideal use cases differ accordingly. Virtual firewall solutions are best suited for cloud-native applications and rapidly changing network infrastructure. In contrast, physical firewalls excel in high-performance scenarios, centralized on-premises security, and protecting legacy systems.

Centralized, On-Premises Networks

Hardware firewalls are architecturally well-suited to centralized, hub-and-spoke model networks. This is because they are implemented as a single security device alongside a single serverstack. Should an enterprise rely on a simple, central network model similar to this, a hardware-based approach can prove effective.

Sprawling, Hybrid Networks

Virtual firewall benefits are best realized when an organization wants to secure sprawling, or cloud-based networks. Virtual firewalls provide a central management hub, even across swathes of an organization’s containerized applications, microservices, and private clouds. This means they are far better suited to hybrid or very distributed network environments, as one single management plane can allow a team to alter rules in different areas of the business. This helps build consistent firewall protection across different zones.

VPN Compatibility

When provisioning access for remote employees, many companies choose Virtual Private Network (VPN) tools. However, because these VPNs encrypt remote workers’ individual connections to internal resources, traditional firewalls can struggle to analyze the encrypted traffic. Both virtual and physical firewalls can effectively analyze VPN traffic, but they have different strengths depending on the network environment and use case.

Virtualized firewalls are a better fit for cloud-based VPN servers – they are also well-suited to new or temporary VPN accounts, such as those set up for temporary work staff and contractors.

Low Budget, or Time

In terms of initial cost and time, a software-based firewall is relatively cheap and rapid to implement. Some come with a free trial, and after that, a relatively low monthly fee. Most virtual firewalls charge based on usage, or throughput, allowing for costs to remain consistent with real usage.

Software-based firewalls are also faster to set up: virtual firewall configuration often requires installation and a few setting tweaks to begin securing traffic. Hardware firewalls, on the other hand, demand physical installation, suitable wiring and space dedication, and proper network positioning and design – changing these down the line then requires the same intensive process.  Plus adding new appliances or devices means electrical and cooling considerations must be taken for each firewall that is installed. On the other hand, public cloud providers are responsible for the physical infrastructure for virtual firewalls.

Data Center Protection

Physical firewall appliances are generally better suited to intensely high-throughput applications, like data centers. This is due to the proximity of their compute power, which can be provided instantaneously from the onboard memory. This also allows for drastic fluctuations in network traffic to be suitably analyzed and processed, with no perceivable impact on latency.

This robust processing capability makes hardware firewalls an ideal choice for organizations experiencing rapid growth or those operating in high-demand sectors where uninterrupted network availability is mission-critical. Some virtual firewall challenges in this use case can include volatile pricing structures and the added latency of traffic being re-routed to a cloud-based analysis engine. Hardware firewalls can be a better fit for data centers since they operate independently from other network components: this frees up server and device resources that can then be fully optimized for their primary network task.