🔒 Azure Firewall – Cloud-Native Firewall for Securing Resources

In today’s cloud-first world, securing resources in Azure is a top priority for organizations. Traditional firewalls are often inadequate for dynamic cloud environments due to scaling and management challenges.

Azure Firewall is a fully managed, cloud-native firewall service designed to protect Azure Virtual Networks, applications, and traffic. It provides stateful packet inspection, threat intelligence, and high availability while integrating seamlessly with other Azure services.

What is Azure Firewall?

Azure Firewall is a layer 4 and layer 7 network security service that protects Azure workloads by controlling inbound and outbound traffic. It operates at the network level, providing granular filtering capabilities to ensure only authorized traffic reaches your resources.

Key capabilities include:

Network and Application Rules: Control traffic based on IP, port, protocol, or fully qualified domain names (FQDNs).
Threat Intelligence-Based Filtering: Block known malicious IPs and domains.
High Availability: Built-in redundancy ensures uptime without additional configuration.
Scalability: Automatically scales to accommodate changing network traffic.
Integration: Works with Azure Monitor, Azure Sentinel, and Security Center for complete security visibility.

Key Features

Stateful Firewall: Tracks connection states for secure network traffic inspection.
Application Rules: Filter outbound HTTP/S traffic using FQDNs.
Network Rules: Control inbound and outbound TCP/UDP traffic by IP and port.
Threat Intelligence: Uses Microsoft threat intelligence to block malicious sources.
Logging and Analytics: Integration with Azure Monitor and Log Analytics.
High Availability and Redundancy: Built-in HA without manual setup.
Secure Hybrid Connectivity: Works with ExpressRoute and VPN Gateway for on-premises traffic.

How Azure Firewall Works

Deployment: Deploy Azure Firewall in a dedicated subnet called AzureFirewallSubnet in a Virtual Network (VNet).
Traffic Flow: All inbound and outbound traffic is routed through the firewall via user-defined routes (UDRs).
Inspection: Azure Firewall inspects traffic based on rules and policies.
Filtering: Traffic matching rules is allowed or denied.
Logging: Logs are sent to Azure Monitor, Log Analytics, or Storage accounts for analysis.

3 Unique Example Programs / Configurations

✅ Example 1: Create Azure Firewall using Azure CLI

# Create Resource Group
az group create --name MyResourceGroup --location eastus

# Create Virtual Network with Firewall Subnet
az network vnet create \
  --name MyVNet \
  --resource-group MyResourceGroup \
  --address-prefix 10.0.0.0/16 \
  --subnet-name AzureFirewallSubnet \
  --subnet-prefix 10.0.1.0/24

# Create Azure Firewall
az network firewall create \
  --name MyFirewall \
  --resource-group MyResourceGroup \
  --location eastus

👉 Deploys a basic Azure Firewall in a dedicated subnet for network security.

✅ Example 2: Configure Network and Application Rules

# Create Firewall Application Rule
az network firewall network-rule create \
  --firewall-name MyFirewall \
  --resource-group MyResourceGroup \
  --collection-name AllowWebApp \
  --name AllowHTTP \
  --protocols TCP \
  --source-addresses 10.0.2.0/24 \
  --destination-addresses 20.30.40.50 \
  --destination-ports 80 443 \
  --action Allow \
  --priority 100

# Create Firewall Application Rule for outbound FQDN
az network firewall application-rule create \
  --firewall-name MyFirewall \
  --resource-group MyResourceGroup \
  --collection-name AllowWebDomains \
  --name AllowMicrosoft \
  --protocols http=80 https=443 \
  --target-fqdns "*.microsoft.com" \
  --source-addresses 10.0.2.0/24 \
  --action Allow \
  --priority 200

👉 Allows HTTP/S traffic to specific IPs and FQDN-based outbound traffic.

✅ Example 3: ARM Template Deployment for Azure Firewall

{
  "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",
  "contentVersion": "1.0.0.0",
  "resources": [
    {
      "type": "Microsoft.Network/azureFirewalls",
      "apiVersion": "2021-05-01",
      "name": "myFirewall",
      "location": "eastus",
      "properties": {
        "sku": {
          "name": "AZFW_VNet",
          "tier": "Standard"
        },
        "ipConfigurations": [
          {
            "name": "fwIpConfig",
            "properties": {
              "subnet": {
                "id": "[resourceId('Microsoft.Network/virtualNetworks/subnets','MyVNet','AzureFirewallSubnet')]"
              },
              "publicIPAddress": {
                "id": "[resourceId('Microsoft.Network/publicIPAddresses','myFirewallPublicIP')]"
              }
            }
          }
        ]
      }
    }
  ]
}

👉 Deploys Azure Firewall with a public IP and dedicated subnet using Infrastructure-as-Code (IaC).

How to Remember Azure Firewall (Exam & Interview Tips)

Mnemonic: “S.T.A.R.S.”

S – Stateful: Tracks active connections for inspection
T – Threat Intelligence: Blocks malicious IPs and domains
A – Application & Network Rules: Granular control of traffic
R – Redundancy & HA: High availability built-in
S – Secure Hybrid Access: Works with ExpressRoute/VPN

Think: “STARS protect your Azure workloads with stateful intelligence.”

Why Learning Azure Firewall is Important

Cloud-Native Security: Protects VNets without third-party appliances.
Granular Traffic Control: Rules at network and application levels.
High Availability: Scales automatically for enterprise workloads.
Integration: Works with Azure Monitor, Sentinel, and Security Center.
Compliance: Helps meet industry regulations and security standards.
Exam Relevance: Core topic for AZ-104, AZ-305, and Azure Security exams.

Real-World Use Cases

Enterprise VNets: Secure traffic between subnets and VNets.
Hybrid Cloud: Protect on-premises to Azure traffic via VPN or ExpressRoute.
Web Applications: Control outbound internet access to FQDNs.
Threat Mitigation: Block traffic from known malicious IPs using Threat Intelligence.
Multi-Region Deployments: Centralized firewall for global VNets.

Best Practices

Always deploy Azure Firewall in a dedicated subnet called AzureFirewallSubnet.
Enable Threat Intelligence-based filtering for added security.
Use application rules for FQDN-based outbound filtering.
Monitor firewall activity with Azure Monitor and Log Analytics.
Combine with Network Security Groups (NSGs) for layered security.

Conclusion

Azure Firewall is a robust, fully managed, cloud-native security service that protects Azure workloads with stateful traffic inspection, granular rules, and threat intelligence.

Key takeaways:

Protects inbound and outbound traffic at network and application layers
Offers built-in high availability and automatic scaling
Integrates seamlessly with Azure Monitor, Sentinel, and Security Center
Supports hybrid cloud scenarios with ExpressRoute or VPN

Mastering Azure Firewall equips you to design secure cloud architectures, manage network traffic efficiently, and succeed in Azure certification exams.

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