Leveraging Azure Firewall for network security involves deploying, configuring, and managing Azure Firewall to secure resources within a Virtual Network (VNet). Azure Firewall is a managed, cloud-based network security service that protects your Azure Virtual Network resources.

Introduction to Azure Firewall

Azure Firewall is a stateful firewall as a service with built-in high availability and unrestricted cloud scalability. It provides network-level protection for all the resources in your Azure Virtual Network.

• Stateful inspection: Azure Firewall is stateful, which means it doesn’t forget past actions; it can make more intelligent decisions based on the context of a stream of packets.
• Built-in high availability: No additional load balancers are needed because high availability is built into the service.
• Scalability: As a cloud-native service, Azure Firewall scales automatically with your network traffic, ensuring you don’t need to worry about capacity planning.

Deployment of Azure Firewall

Step 1: Initial Setup

• Create a Virtual Network (VNet): Before deploying the Azure Firewall, you need a VNet where your resources will be located.
• Create a firewall subnet: In your VNet, create a dedicated subnet for Azure Firewall with the name ‘AzureFirewallSubnet’. This subnet must have at least a /26 CIDR block.

Step 2: Deploy Azure Firewall

• Navigate to the Azure Portal.
• Search for and select “Firewall” in the marketplace.
• Click “Create”, and fill out the necessary information like Name, Region, and Virtual Network.
• Select the appropriate SKU and other options depending on your requirements.

Step 3: Configure the Firewall Route

• Go to the ‘Route tables’ and create or update your route table.
• Add a route that directs all traffic to the Azure Firewall’s private IP address.

Step 4: Update Network Security Groups (NSGs)

• Configure NSGs to allow traffic to flow to and from the firewall.
• Lock down traffic to only what is necessary for your network.

Azure Firewall Configuration

Creating Rules

• Application rules: Used to define fully qualified domain names (FQDNs) that can be accessed from your VNet.
• Network rules: Used to define rules based on IP address, port, and protocol.

Use Azure Firewall Policies

• Firewall Policies is a global resource that enables you to manage and configure your firewalls using rules that can be shared across multiple firewalls.
• You can create and apply threat intelligence, application rules, network rules, and DNS settings via policies.

Integrate with other Azure Services

• Incorporate Azure Firewall with Azure Monitor for logging and analytics.
• Use Azure Security Center for an additional layer of security management and threat protection.

Testing and Monitoring

Testing Your Firewall

• Create test resources behind Azure Firewall and attempt to access them using the allowed and denied configurations to validate the rules.
• Test accessing external services with and without the appropriate application and network rules in place.

Monitoring

• Azure Monitor logs: Use Azure Monitor logs for viewing and analyzing firewall logs.
• Metrics: Azure Firewall provides various metrics which can be used to monitor throughput, health state, and rule counts, among others.
• Threat intelligence: Enable threat intelligence-based filtering to alert and deny traffic from/to known malicious IP addresses and domains.

Cost Management

• Consider the Azure Firewall service tier: Choose between the Standard and Premium tiers based on the necessary feature set and cost implications.
• Analyze traffic patterns: Monitor and analyze your network traffic with Azure Monitor to understand the required scale and manage the associated costs.

Best Practices

• Regularly update rules: Keep the firewall rules updated as per the changing access requirements and threat landscape.
• Restrict outbound traffic: Only allow the necessary outbound traffic; by default, Azure Firewall allows all outbound traffic.
• Implement proper network segmentation: Use subnets and VNets to segment your network; this can limit the lateral movement in case of a security breach.
• Integrate with Azure security best practices: Always follow broader Azure security best practices and integrate Azure Firewall into your overall security posture.

By carefully implementing, configuring, and managing Azure Firewall, you can leverage it to enhance your Azure network security and protect your resources against potential threats. Regular monitoring and adjustments based on traffic patterns and threat intelligence will ensure your firewall remains an effective security tool against evolving threats.