Control: 6.2.2 Ensure that Activity Log Alert exists for Delete Policy Assignment

Description

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

Monitoring for delete 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

Navigate to the Monitor blade.
Select Alerts.
Select Create.
Select Alert rule.
Choose a subscription.
Select Apply.
Select the Condition tab.
Click See all signals.
Select Delete policy assignment (Policy assignment).
Click Apply.
Select the Actions tab.
Click Select action groups to select an existing action group, or Create action group to create a new action group.
Follow the prompts to choose or create an action group.
Select the Details tab.
Select a Resource group, provide an Alert rule name and an optional Alert rule description.
Click Review + create.
Click Create.

From Azure CLI

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

From PowerShell

Create the conditions object

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

Retrieve the Action Group information and store in a variable, then create the 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/delete.

New-AzActivityLogAlert -Name "<activity log 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.

Usage

Run the control in your terminal:

powerpipe control run azure_compliance.control.cis_v300_6_2_2

Snapshot and share results via Turbot Pipes:

powerpipe login
powerpipe control run azure_compliance.control.cis_v300_6_2_2 --share

SQL

This control uses a named query:

with alert_rule as (
  select
    alert.id as alert_id,
    alert.name as alert_name,
    alert.enabled,
    alert.location,
    alert.subscription_id
  from
    azure_log_alert as alert,
    jsonb_array_elements_text(scopes) as sc
  where
    alert.location = 'global'
    and alert.enabled
    and sc = '/subscriptions/' || alert.subscription_id
    and alert.condition -> 'allOf' @> '[{"equals":"Administrative","field":"category"}]'
    and alert.condition -> 'allOf' @> '[{"field": "operationName", "equals": "Microsoft.Authorization/policyAssignments/delete"}]'
  limit 1
)
select
  sub.subscription_id as resource,
  case
    when count(a.subscription_id) > 0 then 'ok'
    else 'alarm'
  end as status,
  case
    when count(a.subscription_id) > 0 then 'Activity log alert exists for delete policy assignment event.'
    else 'Activity log alert does not exists for delete policy assignment event.'
  end as reason
  
  , sub.display_name as subscription
from
  azure_subscription sub
  left join alert_rule a on sub.subscription_id = a.subscription_id
group by
  sub._ctx,
  sub.subscription_id,
  sub.display_name;