Azure Firewall - A Comprehensive Guide

Azure Firewall is a managed, cloud-native network security service that protects resources running in an Azure Virtual Network. It provides centralized policy management and high availability without requiring you to manage the underlying infrastructure.

Key Features of Azure Firewall

• Stateful Filtering — inspects and filters traffic based on rules that track the state of active connections
• Built-in High Availability — no need to configure separate load balancers for the firewall itself
• FQDN Filtering — allows or denies outbound traffic based on fully qualified domain names
• Threat Intelligence — can automatically block traffic to and from known malicious IP addresses and domains
• Centralized Policy Management — using Firewall Policy, rules can be managed centrally across multiple firewalls

How Azure Firewall Works

Azure Firewall is deployed into a dedicated subnet within a Virtual Network. All traffic entering or leaving the network can be routed through the firewall, which evaluates it against network rules, application rules, and NAT rules before allowing or blocking it.

Types of Rules

• Network Rules — control traffic based on source/destination IP, port, and protocol
• Application Rules — control outbound traffic based on fully qualified domain names (FQDNs)
• NAT Rules — translate and filter inbound traffic to internal resources

Common Use Cases

• Centrally securing outbound internet access for multiple virtual networks and subscriptions
• Filtering traffic to specific trusted domains for compliance requirements
• Protecting hub-and-spoke network architectures from a single, centralized firewall in the hub