Cis Azure Compute 2.4.12

Ensure public network access is disabled

Description

Disable public network access to prevent exposure to the internet and reduce the risk of unauthorized access. Use private endpoints to securely manage access within trusted networks.

This recommendation applies to function apps using the Consumption, Premium, or Dedicated (App Service) plans, which support deployment slots.

Rationale

Disabling public network access improves security by ensuring that the service is not directly exposed to the public Internet. This has the added benefit of providing more granular control over security settings and configurations for those additional layers of separation.

Impact

NOTE: Prior to disabling public network access, it is strongly recommended that, for each function app deployment slot, either:

• complete virtual network integration as described in "Ensure app is integrated with a virtual network"

OR

• set up private endpoints/links as described in "Ensure private endpoints are used to access App Service apps."

Disabling public network access restricts direct access to the service. This enhances security but will require the configuration of a virtual network and/or private endpoints for any services or users needing access within trusted networks.

Audit Procedure

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Networking.
6. Under Inbound traffic configuration, ensure that Public network access is set to Disabled.
7. Repeat steps 1-6 for each function app and deployment slot.

Using Azure CLI

Run the following command to list function apps:

az functionapp list

For each function app, run the following command to list deployment slots:

az functionapp deployment slot list --resource-group <resource-group-name> --name <function-app-name>

For each deployment slot, ensure that publicNetworkAccess is set to Disabled.

Expected Result

The publicNetworkAccess property should be set to Disabled.

Remediation

Using Azure Portal

1. Go to App Services or Function App.
2. Click the name of a function app.
3. Under Deployment, click Deployment slots.
4. Click the name of a deployment slot.
5. Under Settings, click Networking.
6. Under Inbound traffic configuration, click the text next to Public network access.
7. Select the radio button next to Disabled.
8. Click Save.
9. Check the box to confirm the change.
10. Click Continue.
11. Repeat steps 1-10 for each function app and deployment slot requiring remediation.

Using Azure CLI

For each deployment slot requiring remediation, run the following command to disable public network access:

az resource update --resource-group <resource-group-name> --name <function-app-name>/slots/<deployment-slot-name> --resource-type "Microsoft.Web/sites" --set properties.publicNetworkAccess=Disabled

Default Value

By default, public network access is enabled.

References

1. https://learn.microsoft.com/en-us/azure/app-service/networking-features
2. https://learn.microsoft.com/en-us/azure/azure-functions/functions-deployment-slots
3. https://learn.microsoft.com/en-us/cli/azure/functionapp
4. https://learn.microsoft.com/en-us/cli/azure/resource

Profile

Level 1 | Automated