Create and configure Azure Firewall

It provides scalable, built-in high availability with unrestricted cloud scalability, which can be crucial when protecting your Azure Virtual Network resources. The service is fully integrated with Azure Monitor for logging and analytics.

Understanding Azure Firewall

Azure Firewall operates at Layer 4 (Transport Layer) of the OSI model, allowing it to filter traffic at an IP level. It offers the following features:

• Stateful firewall as a service
• High availability built-in
• Unrestricted cloud scalability
• Inbound and outbound filtering rules
• FQDN tags
• Network traffic filtering rules
• Outbound SNAT support

Deploying Azure Firewall

Before configuring the Azure Firewall, you first need to create one within your Azure subscription. To deploy Azure Firewall, follow these general steps:

1. Create a Resource Group if you don’t already have one. This will contain all of your Azure Firewall resources.
2. Set Up a Virtual Network and ensure it has a dedicated subnet for Azure Firewall named ‘AzureFirewallSubnet’ with a CIDR of at least /25.
3. Create the Azure Firewall by navigating to the ‘Create a resource’ section, selecting ‘Networking’, and then ‘Firewall’. Follow the creation wizard where you will specify your resource group, region, and other details.
4. Configure the Firewall Policy, which manages rules and settings that govern the behavior of Azure Firewall. You can create a new policy or use an existing one.

Configuring Azure Firewall

Step 1: Configure the Rules

Firewall rules determine the traffic that’s allowed or denied. Types of rules include:

• Network Rules: Allow/Deny based on IP, protocol, and port.
  For example, to allow HTTP traffic to a web server:

  Source Type: IP Address
  Source: Any (or specific IPs)
  Protocol: TCP
  Destination Port: 80
  Destination Address: IP address of the web server

• Application Rules: Allow/Deny based on Fully Qualified Domain Names (FQDN).
  An example to allow outbound HTTPS traffic to *.microsoft.com:

  Target FQDNs: *.microsoft.com
  Protocol: HTTPS
  Port: 443

• NAT Rules: Used for network address translation, particularly useful for global access to private services.

Step 2: Set up Threat Intelligence

Azure Firewall can be configured with Threat Intelligence to alert or deny traffic from/to known malicious IP addresses and domains, which is based on Microsoft’s threat intelligence feed.

Step 3: Integrate with Azure Monitor

Integrate your firewall with Azure Monitor for logging and analytics. It will capture logs related to application rule, network rule, threat intelligence, and more. These logs can be sent to Azure Monitor logs, Azure Storage, or Azure Event Hubs.

Monitoring Azure Firewall

Once your firewall is configured, ongoing monitoring will be crucial. You should continuously review the logs to fine-tune your rules and respond to detected threats.

• Firewall Logs: Detailed information about traffic processed by the firewall.
• Metrics: Provides performance metrics.
• Health: Offers health and availability status.

Cost Considerations

The costs for Azure Firewall are based on two components:

1. Deployment costs: A fixed hourly rate, depending on the tier (Standard or Premium).
2. Processing costs: Based on the amount of data processed by the firewall.

Conclusion

Azure Firewall is a robust solution for network security within the Azure ecosystem. It provides fine-grained controls over network traffic, along with monitoring and logging capabilities that integrate seamlessly with other Azure services. Maintain vigilance over your Azure resources and always keep your firewall rulesets up to date to respond to the evolving landscape of cyber threats.