Are you a guardian of your domain? Lean how to leverage your aptitude in security to protect Microsoft Azure technologies, with a goal of earning the Microsoft Certified: Azure Security Engineer Associate certification!
Securing a virtual network (VNet) involves isolating resources and controlling the flow of traffic between them. A VNet is a private network in Azure, and you divide it into smaller segments called subnets to group resources like web servers or databases. You control traffic flow using Network Security Groups (NSGs), which are rule sets that allow or deny traffic to and from resources based on IP addresses, ports, and protocols. For more granular control, you can use Application Security Groups (ASGs) to define rules based on an application's role, like "WebServers," rather than IP addresses, which makes rules easier to manage as servers scale.
To manage routing and direct traffic through security appliances, you configure User-Defined Routes (UDRs). A route table with UDRs overrides Azure's default system routes, allowing you to send traffic destined for the internet, for example, through a firewall or network virtual appliance (NVA) for inspection before it leaves your network. This creates a hub-and-spoke topology where a central hub VNet contains shared security services, and spoke VNets containing workloads route their traffic through the hub for centralized policy enforcement.
Private access ensures that services are reachable only from within your Azure networks or on-premises networks, not from the public internet. The primary method is Azure Private Link, which provides a private IP address for an Azure service (like a Storage Account or SQL Database) inside your VNet. This means your virtual machines connect to the service's private endpoint using the Azure backbone network, keeping all traffic off the public internet and invisible to outside threats.
To connect your on-premises network to Azure privately, you use a VPN Gateway for an encrypted connection over the internet or Azure ExpressRoute for a dedicated, private fiber connection. Both methods establish a trust boundary extending your corporate network into Azure. Once connected, you can use Virtual Network Peering to link VNets directly, allowing resources in different VNets to communicate using private IP addresses as if they were on the same network, without traversing the public internet.
When resources like web applications must be accessible from the internet, you must secure the public entry points. A public load balancer or an Application Gateway distributes incoming internet traffic to backend pools of virtual machines or other services. The Application Gateway, specifically, is a web traffic load balancer that includes a Web Application Firewall (WAF) to inspect incoming HTTP/HTTPS requests for common attacks like SQL injection or cross-site scripting, acting as a protective shield for your web apps.
For resources like virtual machines that require inbound management ports (like RDP or SSH), you should avoid exposing them directly to the internet. Instead, use the Azure Bastion service, which provides secure and seamless RDP/SSH connectivity through the Azure portal over TLS. This means you connect to the Bastion service, and it then connects to your VM privately, so the VM itself does not need a public IP address or open management ports, significantly reducing its attack surface.
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A Network Security Group (NSG) is a rule set that allows or denies traffic based on IP addresses, ports, and protocols. An Application Security Group (ASG) provides more granular control by defining rules based on an application's role, like 'WebServers,' which makes rules easier to manage as servers scale.
You should use Azure Private Link when you need to ensure a service is reachable only from within your Azure networks or on-premises networks, not from the public internet. It provides a private IP address for the service inside your VNet, keeping all traffic off the public internet and invisible to outside threats.
User-Defined Routes (UDRs) are used to manage routing and direct traffic through security appliances by overriding Azure's default system routes. This allows you to send traffic, like internet-bound traffic, through a firewall or network virtual appliance for inspection before it leaves your network, enabling a hub-and-spoke topology for centralized policy enforcement.
Azure Bastion provides secure and seamless RDP/SSH connectivity through the Azure portal over TLS, so the virtual machine itself does not need a public IP address or open management ports. You connect to the Bastion service, and it then connects to your VM privately, significantly reducing the VM's attack surface.
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