Virtual network enforcement with security admin rules in Azure Virtual Network Manager
In this article, you'll learn how security admins rules provide flexible and scalable enforcement of security policies over tools like network security groups. First, you learn the different models of virtual network enforcement. Then, you learn the general steps for enforcing security with security admin rules.
Virtual network enforcement
With network security groups (NSGs) alone, widespread enforcement on virtual networks across several applications, teams, or even entire organizations can be tricky. Often there’s a balancing act between attempts at centralized enforcement across an organization and handing over granular, flexible control to teams.
Security admin rules aim to eliminate this sliding scale between enforcement and flexibility altogether by consolidating the pros of each of these models while reducing the cons of each. Central governance teams establish guard rails through security admin rules, while still leaving room for individual teams to flexibly pinpoint security as needed through NSG rules. Security admin rules aren't meant to override NSG rules. Instead, they work with NSG rules to provide enforcement and flexibility across your organization.
Enforcement Models
Let’s look at a few common models of security management without security admin rules, and their pros and cons:
Model 1 - Central governance team management with NSGs
In this model, a central governance team within an organization manages all NSGs.
| Pros | Cons |
|---|---|
| The central governance team can enforce important security rules. | Operational overhead is high as admins need to manage each NSG, as the number of NSGs increases, the burden increases. |
Model 2 - Individual team management with NSGs
In this model, individual teams within an organization without a centralized governance team manage their own NSGs.
| Pros | Cons |
|---|---|
| The individual team has flexible control in tailoring security rules based on their service requirements. | The central governance team can't enforce critical security rules, such as blocking risky ports. Individual team might also misconfigure or forget to attach NSGs, leading to vulnerability exposures. |
Model 3 - NSGs are created through Azure Policy and managed by individual teams.
In this model, individual teams still manage their NSGs. The difference is the NSGs are created using Azure Policy to set standard rules. Modifying these rules would trigger audit notifications.
| Pros | Cons |
|---|---|
| The individual team has flexible control in tailoring security rules. The central governance team can create standard security rules and receive notifications if rules are modified. |
The central governance team still can't enforce the standard security rules, since NSG owners in teams can still modify them. Notifications would also be overwhelming to manage. |
Network traffic enforcement and exceptions with security admin rules
Let’s apply the concepts discussed so far to an example scenario. A company network administrator wants to enforce a security rule to block inbound SSH traffic for the whole company. Enforcement of this type of security rule was difficult without a security admin rule. If the administrator manages all the NSGs, then management overhead is high, and the administrator can't rapidly respond to product teams’ needs to modify NSG rules. On the other hand, if the product teams manage their own NSGs without security admin rules, then the administrator can't enforce critical security rules, leaving potential security risks open. Using both security admin rules and NSGs can solve this dilemma.
In this case, The administrator can create a security admin rule to block inbound SSH traffic for all the virtual networks in the company. The administrator can also create a security admin rule to allow inbound SSH traffic for specific virtual networks that need an exception. The security admin rule is enforced across the company, and the administrator can still allow exceptions for specific virtual networks. This is done through the use of priority order for each rule.
The diagram shows how the administrator can achieve the following goals:
- Enforce security admin rules across the organization.
- Allow exceptions for the application team to handle SSH traffic.
Step 1: Create a network manager instance
The company administrator can create a network manager with the root management group of the firm as the scope of this network manager instance.
Step 2: Create network groups for virtual networks
The administrator creates two network groups – ALL network group consisting of all the virtual networks in the organization, and App network group consisting of virtual networks for the application needing an exception. ALL network group in the above diagram consists of VNet 1 to VNet 5, and App network group has VNet 4 and VNet 5. Users can easily define both network groups using dynamic membership.
Step 3: Create a security admin configuration
In this step, two security admin rules are defined with the following security admin configuration:
- a security admin rule to block inbound SSH traffic for ALL network group with a lower priority of 100.
- a security admin rule to allow inbound SSH traffic for App network group with a higher priority of 10.
Step 4: Deploy the security admin configuration
After the deployment of the security admin configuration, all virtual networks in the company have the deny inbound SSH traffic rule enforced by the security admin rule. No individual team can modify the deny rule, only the defined company administrator can. The App virtual networks have both an allow inbound SSH traffic rule and a deny inbound SSH traffic rule (inherited from All network group rule). With a smaller priority number on the allow inbound SSH traffic rule for App network group, the rule is evaluated first. When inbound SSH traffic comes to an App VNet, the higher priority security admin rule allows the traffic. Assuming there are NSGs on the subnets of the App virtual networks, this inbound SSH traffic is next evaluated based on NSGs set by the application team. The security admin rule methodology described here allows the company administrator to effectively enforce company policies and create flexible security guard rails across an organization that work with NSGs.
Next steps
Learn how to block high risk ports with security admin rules
Check out the Azure Virtual Network Manager FAQ