Control: 5.2.1 Ensure that Activity Log Alert exists for Create Policy Assignment

Description

Create an activity log alert for the Create Policy Assignment event.

Monitoring for create policy assignment events gives insight into changes done in "Azure policy - assignments" and can reduce the time it takes to detect unsolicited changes.

Remediation

From Azure Portal

1. Navigate to the Monitor blade.
2. Select Alerts.
3. Select Create.
4. Select Alert rule.
5. Under Filter by subscription, choose a subscription.
6. Under Filter by resource type, select Policy assignment (policyAssignments).
7. Under Filter by location, select All.
8. From the results, select the subscription.
9. Select Done.
10. Select the Condition tab.
11. Under Signal name, click Create policy assignment (Microsoft.Authorization/policyAssignments).
12. Select the Actions tab.
13. To use an existing action group, click Select action groups. To create a new action group, click Create action group. Fill out the appropriate details for the selection.
14. Select the Details tab.
15. Select a Resource group, provide an Alert rule name and an optional Alert rule description.
16. Click Review + create.
17. Click Create.

From Azure CLI

az monitor activity-log alert create --resource-group "<resource group name>"
--condition category=Administrative and operationName=Microsoft.Authorization/policyAssignments/write and level=<verbose | information | warning | error | critical> --scope "/subscriptions/<subscription ID>" --name "<activity log rule name>" -- subscription <subscription ID> --action-group <action group ID> --location global

From PowerShell

Create the conditions object.

$conditions = @()
$conditions += New-AzActivityLogAlertAlertRuleAnyOfOrLeafConditionObject - Equal Administrative -Field category
$conditions += New-AzActivityLogAlertAlertRuleAnyOfOrLeafConditionObject - Equal Microsoft.Authorization/policyAssignments/write -Field operationName $conditions += New-AzActivityLogAlertAlertRuleAnyOfOrLeafConditionObject - Equal Verbose -Field level

Get the Action Group information and store it in a variable, then create a new Action object.

$actionGroup = Get-AzActionGroup -ResourceGroupName <resource group name> -
Name <action group name>
$actionObject = New-AzActivityLogAlertActionGroupObject -Id $actionGroup.Id

Create the Scope variable.

$scope = "/subscriptions/<subscription ID>"

Create the Activity Log Alert Rule for Microsoft.Authorization/policyAssignments/write

New-AzActivityLogAlert -Name "<activity alert rule name>" -ResourceGroupName "<resource group name>" -Condition $conditions -Scope $scope -Location global -Action $actionObject -Subscription <subscription ID> -Enabled $true

Default Value

By default, no monitoring alerts are created.