Cloud-native firewalls vs. IaaS firewalls, honestly compared
Every cloud security design eventually hits this fork: put the firewall layer in the platform’s own managed service — AWS Network Firewall, Azure Firewall, Google Cloud Armor and friends — or drop a virtual appliance from an established vendor (Palo Alto, Fortinet, Check Point, pfSense) onto the platform’s compute and route traffic through it. Vendors on both sides have a tidy story. Neither story survives contact with a real deployment, so here’s the version with the caveats left in.
What each actually is
A cloud-native firewall is a service the provider builds, runs and patches. You write policy against the provider’s own object model — security groups, network security groups, firewall policies, rules resources — and the provider’s control plane handles placement, scaling and availability. You never see or manage the underlying compute.
An IaaS firewall (I’ll call it a virtual appliance, since that’s what it is) is somebody else’s NGFW, shipped as a VM image, that you deploy onto the cloud’s compute and stitch into the network yourself — route tables, load balancers, availability zones, the lot. The vendor didn’t build it for this cloud; you’re overlaying it onto infrastructure it wasn’t born in.
The case for cloud-native
You stop operating infrastructure you don’t need to operate. No patch cadence, no sizing decisions, no capacity planning for a traffic spike at 3am. The provider scales the service; you scale the policy.
It’s integrated by default, not by effort. Native firewall services read from and write to the platform’s own IAM, flow logs, tagging and alerting without a connector, an agent or a second console. Attribution, audit trail and least-privilege access to the firewall’s own control plane come from the same identity system as everything else you run.
Deployment is fast and the failure modes are the provider’s problem. High availability across zones is usually a checkbox, not a design exercise. For a straightforward perimeter or east-west segmentation requirement, you can have a working control in hours, not a project.
The billing model matches the workload. You pay for throughput and rules processed, roughly in line with what you actually use, rather than provisioning a box sized for a peak you might see twice a year.
Where cloud-native falls short
Depth, still, in most cases. A managed cloud firewall is usually strong on L3/L4 filtering and reasonable on basic L7 rules, but application identification, IPS/IDS signature depth, sandboxing, SSL/TLS decryption at scale and the sheer breadth of threat intelligence feeds a mainstream NGFW vendor has spent two decades building are not the same product. This gap narrows every year, but treat “we have a cloud firewall” and “we have an NGFW” as different claims until you’ve checked the feature list for what you actually need.
Multi-cloud means multiple everything. The policy model, the logging format, the rule syntax and the operational quirks differ across providers. A ruleset you understand well on one cloud is a fresh learning curve, not a copy-paste, on another. If your estate spans providers, “cloud-native” quietly becomes “three native things,” each with its own edge cases.
You’re inside the provider’s blast radius and roadmap. A control-plane issue with the service is a control-plane issue for your firewall, full stop, and you have no console to fail over to. You’re also dependent on the provider’s release cadence for features a competitor’s appliance may have shipped years ago.
Cost at genuine scale isn’t always the bargain it looks like at small scale. Rule and throughput-based pricing that looked cheap in a proof of concept can outrun a fixed-capacity appliance once traffic volumes get serious. Model it against your actual numbers, not the vendor’s example.
The case for the virtual appliance
Maturity and depth you can specify. If you need deep application-layer inspection, a particular IPS engine, DLP, or a threat intelligence feed your compliance regime already trusts, a leading NGFW vendor has almost certainly built it, tuned it and supported it in production for years.
One policy model across everywhere you run. The same rulebase, the same logging format, the same management console on-prem, in this cloud and in that one. For an estate that genuinely is hybrid or multi-cloud, this consistency is worth real money in reduced training, reduced mistakes and a single incident response workflow.
Portability, and leverage. The appliance isn’t wedded to one provider’s roadmap or pricing decisions. Moving workloads, or renegotiating with a cloud vendor, doesn’t mean re-learning your firewall.
Where the virtual appliance costs you
You now own everything the provider used to own. Patching, licence renewal, capacity planning, and — the part people underestimate — designing genuine high availability yourself: active/passive or active/active pairs, health checks, failover timing, and what happens to in-flight sessions when it fails over. Get this design wrong and the firewall becomes the single point of failure it was supposed to prevent.
It’s a bottleneck you built. All that traffic now hairpins through a device (or pair of devices) sized for a load you estimated in advance. Scaling it under real traffic growth is a capacity project, not a slider.
Integration is work, not a default. Getting the appliance’s logs into the cloud’s native monitoring, its identity into the cloud’s IAM, its deployment into the cloud’s infrastructure-as-code, is entirely on you. It’s achievable, and often achievable well, but it’s effort the cloud-native option doesn’t ask for.
Licence cost stacks on top of compute cost, and neither shrinks just because the box is idle overnight.
How I’d actually decide
Not with a platform preference. With the question a proportionate design always starts from: what’s the actual risk, and what’s the actual requirement?
- If the estate is single-cloud, the requirement is perimeter control and reasonable segmentation, and nothing on the compliance or threat model demands a specific NGFW capability — use the cloud-native service. It’s less to build, less to patch, and less to get wrong, and “unused capability” isn’t a virtue if nobody’s using the extra depth anyway.
- If you’re genuinely multi-cloud or hybrid, or a named requirement (a specific IPS engine, an existing vendor relationship your compliance regime already trusts, application-layer depth you’ve actually justified) can’t be met natively — the virtual appliance earns its operational overhead. Just design the HA properly, and budget the ongoing ops time honestly, not just the licence cost.
- If you’re not sure which camp you’re in: that’s usually a sign the requirement hasn’t been written down yet, and the platform choice is being made instead of it. Write the requirement down first.
Neither option is a security posture on its own. The firewall, of either kind, is one control in a design; picking the fashionable one and skipping the requirement is exactly the failure mode a proportionate approach exists to avoid.
- cloud
- firewalls
- networking
- architecture