Azure Firewall vs NSG: What to Choose in 2025?

It goes without saying that network security is a crucial need for contemporary cloud applications. With so many security tools and appliances available, it can be challenging to choose the optimal protection for a given use case. For instance, two common security solutions for Azure cloud workloads are Azure Firewall and Azure Network Security Groups (NSG), yet their functions are very different.

To further your understanding of Azure security, I'll compare Azure Firewall and NSG in-depth in this post. I'll examine the use scenarios in addition to contrasting the capabilities of Azure Firewall and NSG so you can choose the one that best suits your needs.

What is Azure Firewall?

Workloads from OSI layers 3 to 7 are secured by the cloud-based, fully-managed intelligent firewall known as Azure Firewall.

By evaluating the network traffic itself to determine whether the incoming/outgoing traffic is malicious, Azure Firewall goes beyond the conventional security strategy of permission based on IP, port, and protocol. Threat intelligence and signature-based IDPS are just a couple of the things this fully managed, highly available cloud service has to offer. Microsoft's preferred solution for safeguarding workloads on Azure Cloud is Azure Firewall.

Key features and capabilities of Azure Firewall include:

1. Stateful Packet Inspection: Azure Firewall can inspect traffic at the network and transport layer, allowing it to make access decisions based on source and destination IP addresses, ports, and protocols. This provides basic network-level filtering.
2. Application Layer Filtering: Azure Firewall goes beyond traditional firewalls by providing application-level filtering. It can control traffic based on fully qualified domain names (FQDNs) and application protocols, giving you more granular control over network access.
3. Centralised Management: Azure Firewall can be centrally deployed and managed, making it easier to enforce consistent security policies across multiple Azure virtual networks and resources. This centralisation simplifies rule management and monitoring.
4. Threat Intelligence: Azure Firewall integrates with threat intelligence feeds to block known malicious IP addresses and domains, enhancing your network's security posture.

What is Azure NSG?

A firewall called an Azure Network Security Group (NSG) operates on levels 3 and 4 of the OSI model. It makes it extremely easy to associate Network Security Groups with a VNet or VM network interface.

NSG is frequently installed for particular vNets, subnets, and network interfaces for virtual machines to refine traffic, in contrast to Azure nsg vs firewall, which monitors all traffic for workloads. It does this by turning on an Access Control List (ACL) or rule (allow or deny), which permits or prohibits traffic to Azure resources.

Key characteristics and features of Azure NSG include:

1. Traffic Filtering: NSGs enable you to filter network traffic at the network level. You can specify rules to allow or deny traffic based on IP addresses, ports, and protocols. This helps you control which traffic can reach your Azure resources.
2. Stateful Inspection: NSGs are stateful, meaning they keep track of the state of connections. When you allow outbound traffic for a specific connection, the corresponding inbound response traffic is automatically permitted, making it easier to define rules.
3. Application Layer Filtering: While NSGs primarily operate at the network layer, you can achieve some application-level filtering by specifying rules based on port numbers. For example, you can allow or deny traffic on specific application ports.
4. Association with Resources: You can associate NSGs with Azure resources like VMs or subnets. This allows you to apply network security rules directly to the resources that need protection.

Azure Firewall vs NSG: Head-to-Head Comparison

Parameters	Azure Firewall	Network Security Group (NSG)
Description	Managed firewall with extensive packet inspection features that are highly available, strong, and intelligent.	a fundamental/traditional firewall built on a 5-tuple hash
Threat detection and blocking	Supports real-time threat detection	Filters traffic based on allow and block rules
FQDN tag support	Supports FQDN tags	Does NOT support FQDN tags
Layers of Protection	provides workload protection by evaluating OSI layers 3 through 7.	basic OSI layer 3 and layer 4 traffic filtering
Availability Zones	Supports Availability Zones	Does NOT support or require Availability Zones
Cost	Azure firewall cost starts at $1.25/hour, excluding data processing charges	Free but standard data ingress/egress costs apply

Difference Between Azure Firewall and NSG (Network Security Group)

1. Azure Firewall vs NSG: Traffic Inspection 

Azure Firewall: Azure firewall configuration is a fully stateful firewall as a service that can perform deep packet inspection of network traffic. It allows you to create rules based on application and network-level criteria, enabling an Azure Solution Architect associate to control and inspect both inbound and outbound traffic. It supports Application Rule collections to allow or deny traffic based on FQDN (Fully Qualified Domain Name) and port.

NSG: Network Security Groups are primarily stateful packet filters. They enable traffic filtering based on source and destination IP addresses, ports, and protocols. While they provide rudimentary network traffic filtration, they need advanced capabilities like deep packet inspection or application-level scrutiny.

2. Azure Firewall vs NSG: Integration 

Azure Firewall: Azure Firewall seamlessly incorporates into the broader Azure ecosystem, allowing for centralised management and close integration with Azure's native security services. This tight integration simplifies the orchestration of security policies across your Azure resources and enhances monitoring and threat detection capabilities.

NSG: NSGs, while effective at their core purpose of network security, function more as standalone entities applied directly to specific virtual machines or subnets. Their integration could be more centralised compared to Azure Firewall and may necessitate additional configurations to achieve comprehensive security coverage across your Azure environment.

3. Azure Firewall vs NSG: Application Visibility 

Azure Firewall: azure firewall vs nsg vs application gateway provides detailed application-level visibility. It can identify and control traffic based on application protocols and FQDNs. This allows you to define rules that are more granular and application-specific.

NSG: NSGs do not provide application-level visibility. They operate at the network level, making it challenging to differentiate between applications or services based solely on NSG rules.

4. Azure Firewall vs NSG: Dynamic Rule Updates 

Azure Firewall: Azure Firewall supports dynamic rule updates. You can create and update rules based on FQDN tags, and it integrates with Azure Firewall Manager for centralised rule management across multiple Azure regions and subscriptions.

NSG: NSGs support rule updates, but they are typically applied statically. You can update NSG rules through the Azure portal, PowerShell, or Azure CLI, but the process is more dynamic and centralised than Azure Firewall's rule management.

5. Azure Firewall vs NSG: Advanced Threat Protection 

Azure Firewall: Azure Firewall includes threat intelligence-based filtering capabilities and integrates with Azure Security Center for advanced threat protection. It can block known malicious traffic and provide alerts for suspicious activities.

NSG: NSGs do not offer advanced threat protection capabilities on their own. You would need to rely on other Azure security services like Azure Security Center for threat detection and protection.

6. Azure Firewall vs NSG: Deployment Flexibility 

Azure Firewall: Azure Firewall offers centralised deployment and management, providing a single point of control for network traffic across multiple Azure resources. This centralised approach simplifies security policy orchestration and monitoring, making it well-suited for scenarios where uniform network security is paramount.

NSG: NSGs provide more granular deployment flexibility. They can be applied directly to individual virtual machines (VMs) or subnets, allowing for fine-grained control over network security rules. This level of flexibility proves valuable in situations where specific, resource-level security configurations are required.

7. Azure Firewall vs NSG: Performance Impact 

Azure Firewall: Azure Firewall is designed for high-performance network security and can scale to handle traffic for large deployments. It offers options for higher throughput and can handle complex rule sets.

NSG: NSGs have a lower performance impact compared to Azure firewalls basic because they primarily operate at the network level. However, complex rule sets, or excessive rule evaluations can impact performance to some extent.

How are They Similar? 

NSGs and Azure Firewall complement each other extremely well and are not redundant with one another. NSGs are often preferred when securing network traffic entering or leaving a subnet. As an illustration, consider a subnet that has virtual machines (VMs) that need RDP connectivity (TCP over 3389) from a Jumpbox. The answer to filtering traffic coming into a VNet from the outside is Azure Firewall. 

It ought to be set up in a separate VNet and kept separate from other resources as a result. Highly available for nsg vs firewall automatically scales to meet the demands of the workload. So that there is room for new VMs that are produced as it scales out, it should be on a subnet of size 26.

The Azure Firewall in the Hub VNet of the model mentioned above has peer connections to two Spoke VNets. The Azure Firewall, which acts as a gateway device, is the User Defined Route (UDR) that points to the Spoke Vnets' subnets even though they are not directly linked. 

In addition, Azure Firewall, which has a public interface, is in charge of securing both incoming and outgoing traffic to the VNet. Applications rules, SNAT, and DNaT are useful in this situation. In a straightforward setting, an nsg firewall ought to be adequate for network protection.

What Should You Choose Between Azure Firewall and NSG? 

When deciding between Azure Firewall and Network Security Groups (NSGs) in Azure, your choice should revolve around the specific requirements of your network security and the nature of your deployment. You can also learn Cloud Computing for beginners, as it would help you to choose wisely.

Azure Firewall is an ideal choice if you need comprehensive traffic inspection capabilities, including deep packet inspection and application-level filtering. It excels in integration with the broader Azure ecosystem, providing centralised management and tight integration with Azure's native security services. This makes it particularly valuable when you require uniform security policies across your Azure resources and when advanced threat protection and application visibility are critical.

On the other hand, NSGs offer a different level of flexibility. They are more suited for scenarios where you need granular control at the network level. You can apply NSGs directly to individual virtual machines or subnets, allowing for customised security configurations tailored to specific resources. NSGs typically offer a more budget-friendly option with reduced intricacy, rendering them suitable for straightforward network security needs.

The Bottom Line

Microsoft provides security services like Azure Firewall and NSG. Instead of asking whether to utilise Azure Firewall or NSG, ask yourself how to get the most out of each service. They are frequently combined to provide a safe atmosphere. By enrolling as a KnowledgeHut Azure Solution Architect Associate, you can get a detailed overview of which is better for you. The use case and security design will choose which to utilise. Cost, skill level, and overall needs are all important considerations when making decisions.

NSG is a suitable choice when your primary goal is network security through traffic allowance or restriction at the network layer. It stands out due to its cost-effectiveness, straightforwardness, and ease of administration. Azure Firewall often becomes the preferred solution for scenarios demanding greater sophistication.