Azure Firewall: Cloud-Native Network Security for Your Azure Infrastructure
By Pooja | 16th July 2025
Introduction
As enterprises rapidly migrate to the cloud, network security becomes a core priority. Traditional firewalls are not designed for cloud-native, scalable, dynamic environments. Microsoft’s Azure Firewall provides a stateful, cloud-native firewall service that’s deeply integrated with Azure and designed to protect your cloud workloads.
Whether you’re securing hybrid networks, implementing zero trust, or enforcing fine-grained traffic filtering, Azure Firewall delivers enterprise-grade protection, high availability, and rich analytics—all managed as a service.
This article provides a complete overview of Azure Firewall, from architecture and features to deployment and use cases.
What is Azure Firewall?
Azure Firewall is a fully managed, stateful network firewall provided by Microsoft Azure. It is designed to control both inbound and outbound network traffic for Azure VNets and hybrid cloud environments. Unlike traditional hardware firewalls, Azure Firewall is a cloud-native service that automatically scales with your network demands.
It offers:
- Centralized policy management
- Threat intelligence filtering
- FQDN and domain-based filtering
- Application and network rule processing
- High availability and disaster recovery
Azure Firewall supports both IPv4 and IPv6 traffic, ensuring modern protocol compatibility.
Why Use Azure Firewall?
Organizations use Azure Firewall for several critical reasons:
- Centralized traffic control across multiple subnets or VNets
- Application-aware filtering (HTTP/S, SQL, etc.)
- Outbound internet access control using FQDNs or domain names
- Threat detection and blocking with Microsoft threat intelligence
- Logging and monitoring via Azure Monitor and Sentinel
- Support for hybrid networks and cross-region deployments
Compared to NSGs or basic load balancer NAT rules, Azure Firewall provides deeper, more granular control and better security posture.
Key Features
Feature | Description |
Stateful Firewall | Remembers traffic sessions to permit related traffic responses |
High Availability | Built-in with 99.95% SLA; no additional configuration needed |
Threat Intelligence | Block or alert traffic from known malicious IPs/domains |
FQDN Filtering | Filter traffic based on domain names, not just IP addresses |
Application Rules | Filter by URL, domain, and protocol (HTTP/S, MSSQL) |
Network Rules | Filter by IP, port, and protocol (TCP/UDP/ICMP) |
Logging and Diagnostics | Integration with Azure Monitor, Log Analytics, and Network Watcher |
Hybrid Connectivity | Works with VPN, ExpressRoute, and virtual WAN |
SNAT & DNAT | Support for source and destination NAT |
Azure Firewall Architecture
Azure Firewall is deployed into a dedicated subnet named AzureFirewallSubnet inside a VNet. It uses:
- Public IP: For outbound SNAT
- Private IP: For internal or hybrid routing
- Route Tables (UDRs): To force traffic through the firewall
Example architecture:
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User -> App Gateway -> Azure Firewall -> Subnet A/B/C -> Internet or On-prem
Azure Firewall can be deployed in:
- Hub-and-spoke topology
- Virtual WAN architecture
- Single VNet model
Azure Firewall vs Network Security Group (NSG)
Feature | Azure Firewall | NSG (Network Security Group) |
Layer | L3–L7 (Application + Network) | L3–L4 (IP + Port) |
Stateful | Yes | Yes |
FQDN Filtering | Yes | No |
Threat Intelligence | Yes | No |
DNAT/SNAT | Yes | No |
Logging and Analytics | Advanced | Basic (via NSG flow logs) |
Use Case | Central security control | Lightweight subnet/VM-level filtering |
Use NSG for basic access control and Azure Firewall for centralized, policy-driven traffic filtering.
Azure Firewall vs Azure WAF (Application Gateway)
Feature | Azure Firewall | Azure WAF (Web Application Firewall) |
Protocol | Any (TCP, UDP, ICMP, etc.) | HTTP/HTTPS only |
Focus | Network & Application access | Web-layer protection (OWASP rules) |
FQDN Support | Yes | Yes |
Threat Protection | Yes | Yes (Web attacks) |
Use Case | Internal/External traffic control | Web app protection |
Use Azure Firewall for network security and Azure WAF for web app-level security.
Types of Azure Firewall
- Azure Firewall Standard
- Baseline offering with L3–L7 traffic control
- Supports threat intelligence, SNAT/DNAT, and custom rules
- Azure Firewall Premium
- Includes TLS inspection, IDPS (Intrusion Detection and Prevention System), and URL filtering
- Ideal for high-security environments and regulated industries
Azure Firewall Policy
Azure Firewall Policy allows centralized rule management:
- Define policies once, apply across multiple firewalls
- Use rule collections: DNAT, Network, Application
- Apply custom priorities
- Reuse policies across regions and subscriptions
Policies support:
- Rule hierarchy
- Multiple public IPs
- Target FQDNs and protocols
Rule Types in Azure Firewall
- Application Rules
- Filter based on FQDN or domain
- Ports: HTTP, HTTPS, MSSQL
- Example: Allow *.microsoft.com
- Network Rules
- Filter by IP address, protocol (TCP/UDP/ICMP), and port
- Example: Allow TCP 1433 to SQL server
- NAT Rules
- DNAT: Redirect incoming public traffic to private IPs
- SNAT: Translate internal IPs to public IPs for outbound access
Each rule collection has a priority to determine processing order.
Deployment Models
- Hub-and-Spoke
- Central firewall in a hub VNet
- Spoke VNets route through firewall via UDR
- Ideal for enterprise-scale networks
- Virtual WAN
- Firewall is integrated with Azure VWAN
- Manages branch and region-based routing
- Simplifies global security
- Standalone
- Deployed inside a single VNet
- Used for isolated workloads or testing
Monitoring and Logging
Azure Firewall integrates with:
- Azure Monitor for metrics and alerts
- Log Analytics for deep querying
- Storage Accounts for long-term logs
- Event Hub for SIEM integration
- Azure Sentinel for threat analytics
Logs include:
- Rule matches
- Connection attempts
- Threat intelligence events
Common Use Cases
- Secure Internet Access
Filter outbound traffic from private VMs using FQDN filtering.
- Web Server Protection
Use DNAT to route traffic to backend VMs securely.
- Hub-Spoke Segmentation
Control traffic between applications in spoke VNets.
- Hybrid Network Integration
Secure traffic between Azure and on-prem using VPN/ExpressRoute.
- Threat Intelligence Blocking
Automatically block known malicious IPs and domains.
Pricing Overview
Azure Firewall charges are based on:
- Deployment Type: Standard or Premium
- Firewall Hours: Fixed cost per deployment per hour
- Data Processed: Pay per GB
- Policy usage (optional)
You can estimate costs with the Azure Pricing Calculator.
Best Practices
- Deploy in a dedicated subnet (AzureFirewallSubnet)
- Use centralized Firewall Policies
- Route all traffic through the firewall using User Defined Routes (UDRs)
- Integrate with Azure Sentinel for security insights
- Regularly review logs for unusual activity
- Combine with NSGs for layered security
- Use Availability Zones for high resilience
- Enable diagnostics logs for visibility
Conclusion
Azure Firewall provides a scalable, intelligent, and cloud-native solution for managing your Azure network security. Its deep integration with Azure services, built-in threat intelligence, centralized policy management, and stateful inspection make it the ideal choice for protecting enterprise cloud environments.
Whether you’re looking to secure outbound traffic, prevent unwanted internet access, or enforce strict traffic filtering between application layers, Azure Firewall delivers the tools to do so—efficiently, securely, and at scale.
As cloud adoption increases, understanding and properly deploying Azure Firewall is essential for robust network protection, compliance, and business continuity
for more detail about Azure Application Gateway