Ensure Only Approved Extensions Are Installed (Manual)

Overview

Only install organization-approved extensions on VMs.

Cyscale lists all VMs with any extension installed. Please review them and exempt the VMs with approved extensions.

Rationale

Azure virtual machine extensions are small applications that provide post-deployment configuration and automation tasks on Azure virtual machines. These extensions run with administrative privileges and can access anything on a virtual machine. The Azure Portal and community provide several such extensions. Each organization should carefully evaluate these extensions and ensure that only those approved for use are implemented.

Remediation guidance

From Azure Console

Open the VM using the Open in Azure button
Go to Settings
Click on Extensions
If there are unapproved extensions, uninstall them.

From Azure Command Line Interface

List the installed extensions for the VM:

az vm extension list --vm-name <vmName> --resource-group <resourceGroupName> --query [*].name

Delete the extensions that are not approved:

az vm extension delete --resource-group <resourceGroupName> --vm-name <vmName> --name <extensionName>

Default Value

By default, no extensions are added to the virtual machines.

References

Multiple Remediation Paths

Azure

SERVICE-WIDE (RECOMMENDED when many resources are affected): Assign Azure Policy initiatives at management group/subscription scope and trigger remediation tasks.

az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

ASSET-LEVEL: Apply the resource-specific remediation steps above to the listed non-compliant resources.

PREVENTIVE: Embed Azure Policy checks into landing zones and IaC workflows to block or auto-remediate drift.

References for Service-Wide Patterns

Azure Policy overview: https://learn.microsoft.com/en-us/azure/governance/policy/overview
Azure Policy remediation: https://learn.microsoft.com/en-us/azure/governance/policy/how-to/remediate-resources
Azure Policy initiative structure: https://learn.microsoft.com/en-us/azure/governance/policy/concepts/initiative-definition-structure

Operational Rollout Workflow

Use this sequence to reduce risk and avoid repeated drift.

1. Contain at Service-Wide Scope First (Recommended)

Azure: assign policy initiatives at management group/subscription scope and run remediation tasks.

az policy assignment create --name <assignment-name> --scope /subscriptions/<subscription-id> --policy-set-definition <initiative-id>
az policy remediation create --name <remediation-name> --policy-assignment <assignment-id>

2. Remediate Existing Affected Assets

Execute the control-specific Console/CLI steps documented above for each flagged resource.
Prioritize internet-exposed and production assets first.

3. Validate and Prevent Recurrence

Re-scan after each remediation batch.
Track exceptions with owner and expiry date.
Add preventive checks in IaC/CI pipelines.

Query logic

These are the stored checks tied to this control.

Azure VMs with extensions

Connectors

Microsoft Azure

Covered asset types

Expected check: eq []

{
  vms(where: { NOT: { extensions_SOME: null } }) {
    ...AssetFragment
  }
}