Azure NSG Overview: Strengthening Your Cloud Security

What is Azure Network Security Group?

Azure network security is a group of access control rules to secure a virtual network or a subnet. These rules monitor outgoing and incoming traffic to determine whether to reject or accept a package.

Azure network security is created at the subnet-level network security group and the VM-level network security group.

• Users can turn on any security rules to create the Azure NSG on or off.
• Azure security groups, which Microsoft entirely manages, assist in straining traffic from and to Azure VNet.
• A five-tuple hash is utilized to monitor the effectiveness of these rules.
• The 5-tuple hash uses the destination port number, IP address, IP addresses, source port number, and other factors.
• Thanks to the functionality of its OSI layers 4 and 3, you can rapidly line NSG with a VM or VNet network interface.

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How does Azure Network Security work?

The Azure network security works in the following ways:

• It is a fantastic option to safeguard virtual networks.
• With this application, network administrators can instantly filter, organize, regulate, and direct multiple traffic flows.
• When creating Azure NSG, you can configure multiple outgoing and incoming rules to disallow or allow specific traffic.
• You must configure and build individual rules to use Azure network security groups.
• Many Azure service resources can be included in the Azure virtual network.
• The complete list that might be put into any virtual network is available under services.
• Zero or one network security group can be configured for every network, interface, and virtual network subnet in a virtual machine.
• You can connect as many network interfaces and subnets as you like to the same network security group.

Based on the circumstances, you can create any rules you like.

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Azure NSG Flow Log Use Cases

Azure NSG flow log use cases provide the insights required to track your environment for compliance, performance, and security. By monitoring data on the present state of your virtual network, they offer crucial information, like where the connections are coming from, what services include connections, and which ports are accessible to the Internet. You can integrate Azure flow logs in various use cases, for instance:

Network Monitoring

• Identify suspicious or unknown network traffic.
• Integrate filtering by port and IP to baseline application behavior.
• Track traffic levels and bandwidth consumption
• Export log data for live or reporting monitoring dashboard feeds 

Compliance

• Verify if your traffic rules align with network compliance and isolation obligations.

Usage Monitoring and Optimization

• Identify your network's top talkers.
• Identify across regions and traffic and integrate Geo–IP.
• Use flow log data for capacity forecasting.
• Fetch and resolve unoptimized traffic rules.

Security Analysis and Network Forensics

• Analyze network flow from suspicious network interfaces or IPs
• Export flow log data to SIEM or IDS

How to Create a Network Security Group in Azure?

To make a network security group in Azure, follow the process mentioned below:

Step 1: Open the Microsoft Azure portal and sign in. Now, search for the network security group and tap on it.

Step 2: Tap on 'create. ' Mention the details in the Azure portal and tap on 'review + create.' Now tap on 'create.'

Step 3: Once you successfully create NSG, tap on 'go-to resource.'

Step 4: To connect your NSG with an interface or a subnet, tap on the 'subnets' service on the left menu under the settings section. Now locate and tap on the 'associate' button, choose a virtual network you are willing to associate with your Azure NSG and tap 'OK.'

Understanding how NSG works in a VM:

Step 5: After signing in to the Microsoft Azure portal, check on the virtual machine. Now tap on 'create' and choose Azure virtual machine.

Step 6: Enter and select the consideration for your VM. Select the resource group and subscription for your VM. Give your VM a unique name and choose the region where you will host it. 

• Also, select the number of available zones for your VM. Image selection is another significant step; you can choose any image.
• Now, select a size according to your needs. Enter the password and username for the VM. These conditions let you access your VM from anywhere. Now select RDP for inbound and port rule, and tap on 'review + create.'

Step 7: Once you configure the virtual machine resources, review the configuration resources and tap 'create' to confirm that you are creating a virtual machine. Recheck your VM configuration and tap on 'create.'

Step 8: Once you successfully create a VM, tap on 'go-to resource.' Now tap 'connect' and click 'download RDP file.'

Step 9:

• Click on the downloaded file.
• Offer the required permissions.
• Enter your VM password and tap 'OK.'

Congratulations! Now, you can access your VM.

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How Azure Network Security Groups Filter Network Traffic?

Network traffic from and to Azure resources can be filtered in an Azure virtual network via the Azure network security group. A Network Security Group (NSG) includes security rules that allow or deny outbound network traffic to and inbound network traffic from specific types of resources in Azure. You need help finding each rule's destination, source, protocol, and port.

Resources from multiple Azure services are deployed into an Azure virtual network. For a detailed list, look for services that might be installed in a virtual network. Each network interface or virtual network subnet in a virtual machine might have one or zero network security group assigned. You can assign the same network security group to multiple subnets and network interfaces you select.

Azure manages outgoing and inbound rules for network security groups in the following ways:

Inbound Traffic

Azure operates its rules first if a network security group is linked to a subnet. However, Azure operates its rules second if a network security group is linked to a network interface. This is also applicable to traffic in a single subnet. Hence, inbound rules manage incoming traffic to the services, permitting administrators to specify the incoming connections to be blocked or allowed.

Outbound Traffic

If a network security group is linked to any network interface, Azure first executes the rules in that particular group, and then the rules are processed in a network security group linked to any existing subnet. Traffic in a single subnet is also included. In Outbound traffic, the data flow is restricted from going outside to prevent its collection by unsecured networks and authorized users.

Intra-subnet Traffic

It promotes creating communication between the resources in the same virtual network or subnet. It often acknowledges trusted traffic but still needs to track and ensure potential security measures to avoid security breaches or authorized access.

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Azure Network Security Group Rules

The Azure network security group rules include the following:

• Deny All InBound: This denial-all rule blocks complete inbound traffic to the VM and offers protection from malicious access outside Azure Vnet.
• Allow Vnet InBound: This rule permits all hosts to communicate without getting blocked within the virtual network.
• Allow Azure LoadBalancer InBound: This rule allows communication with the Azure load balancer with the virtual machine and forward heartbeats.

Azure Network Security Group Best Practices

Azure NSG best practices include the following:

• Before creating a virtual network, plan and create a network, including security rules and network topology.
• Use descriptive tag names for security rules and NSG
• Audit and review the network
• Reject all traffic, then permit the required traffic for the network.
• Test your network before deploying.
• NSG flow logging function is available in the Azure Netwerk observer.
• Logs are forwarded to the storage server,  specified by you in the setup, as soon as the flow logging gets activated.
• The data of the flow log is presented in JSON format.
• Based on the per-basis rule, the output shows the flow for both departing and incoming data.

Conclusion

In Azure, network security groups are highly recognized for assisting you in managing network security instantly and effectively. Application security groups and service tags can help even when setting them up initially is time-consuming. This article elaborates on creating NSG in Azure and the practical use of network security groups. 

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FAQs

Q1. What is the difference between Azure NSG and VNet?

Azure NSG filters outbound and inbound traffic to subnets, network interfaces and VMs. However, Azure VNet enables different types of Azure resources to communicate securely with the on-premises network and the Internet.

Q2. What's the difference between an NSG and an Azure Firewall?

NSG assists in filtering network traffic among Azure resources in a VN (Virtual Network). However, Azure Firewall is a fantastic service firewall offering threat protection for Azure workloads.