Application Security Groups (ASGs) and Network Security Groups (NSGs) are two important tools available in Azure to enhance the security of your deployments. ASGs provide application-centric security by enabling fine-grained control over network traffic between different tiers of an application. On the other hand, NSGs offer network-level security by controlling traffic flow within subnets, between subnets, and between virtual networks.
By leveraging ASGs and NSGs in your Azure environment, you can establish a robust security posture that protects your applications and network infrastructure from unauthorized access and potential threats. Understanding each group’s differences and appropriate use cases is crucial in implementing an effective security strategy on Azure.
Key Differences between ASGs and NSGs
- Layer of Operation: ASGs operate at the transport layer (Layer 4), while NSGs operate at both the network layer (Layer 3) and the transport layer (Layer 4).
- Scope: ASGs are primarily used for managing security between different application tiers, while NSGs focus on network-level security, controlling traffic flow within subnets, between subnets, and between virtual networks.
- Granularity: ASGs offer granular control over network traffic by allowing rules based on source and destination IP addresses and source and destination ports. NSGs provide broader network-level control, including protocol-based filtering.
- Application vs. Network: ASGs are tailored for securing application components and enforcing policies specific to application tiers. NSGs, on the other hand, are designed for securing network infrastructure and implementing network-level security policies.
Network Security Group
- A network security group is used to enforce and control network traffic.
- Controls the inbound and outbound traffic at the subnet level.
- Rules are applied to all resources in the associated subnet.
- Has separate rules for inbound and outbound traffic.
- NSG has a limit of 1000 rules.
- Supports ALLOW and DENY rules.
- Not allowed to specify multiple IP addresses and IP address ranges in the NSG created by the classic deployment model.
Application Security Group
- An application security group is an object reference within an NSG.
- Controls the inbound and outbound traffic at the network interface level.
- Rules are applied to all ASGs in the same virtual network.
- Has separate rules for inbound and outbound traffic.
- ASGs that can be specified within all security rules of an NSG have a limit of 100 rules.
- Supports ALLOW and DENY rules.
- Not allowed to specify multiple ASGs in the source or destination.
