Cis Azure Compute 2.6

Ensure App Service Environment is deployed with an internal load balancer

Description

App Service Environment apps should not be reachable over public internet. To ensure apps deployed in an App Service Environment are not accessible over public internet, one should deploy App Service Environment with an IP address in virtual network. To set the IP address to a virtual network IP, the App Service Environment must be deployed with an internal load balancer.

Rationale

Disabling public network access improves security by ensuring that a service is not exposed on the public internet.

Impact

Disabling public network access restricts access to the service. This enhances security but may require the configuration of private endpoints for any services or users needing access within trusted networks.

Audit Procedure

Using Azure Portal

1. Go to App Service Environments.
2. For each App Service Environment, ensure that Virtual IP Type is set to Internal.

Using Azure CLI

Run the following command to list App Service Environments:

az appservice ase list

For each App Service Environment, ensure that internalLoadBalancingMode is not set to None.

Expected Result

The internalLoadBalancingMode should not be set to None. The Virtual IP Type should be Internal.

Remediation

It is not possible to change the virtual IP configuration of a deployed App Service Environment.

When deploying an App Service Environment, next to Virtual IP, select Internal: The endpoint is an internal load balancer (ILB ASE).

Default Value

When deploying an App Service Environment, Internal: The endpoint is an internal load balancer (ILB ASE) is the default selected option for Virtual IP.

References

1. https://learn.microsoft.com/en-us/azure/app-service/environment/creation

Profile

Level 2 | Automated