CIS.M365.1.3.4 - (L1) Ensure 'User owned apps and services' is restricted

Contributed by Benjamin Metz with -MynsterAll contributors →

Overview

1.3.4 (L1) Ensure 'User owned apps and services' is restricted

By default, users can install add-ins in their Microsoft Word, Excel, and PowerPoint applications, allowing data access within the application.

Do not allow users to install add-ins in Word, Excel, or PowerPoint.

Rationale

Attackers commonly use vulnerable and custom-built add-ins to access data in user applications.

While allowing users to install add-ins by themselves does allow them to easily acquire useful add-ins that integrate with Microsoft applications, it can represent a risk if not used and monitored carefully.

Disable future user's ability to install add-ins in Microsoft Word, Excel, or PowerPoint helps reduce your threat-surface and mitigate this risk.

Impact

Implementation of this change will impact both end users and administrators. End users will not be able to install add-ins that they may want to install.

Remediation action

1. Navigate to Microsoft 365 admin center.
2. Click to expand Settings select Org settings.
3. In Services select User owned apps and services.
4. Uncheck Let users access the Office Store and Let users start trials on behalf of your organization
5. Click Save.

PowerShell

1. Connect to the Microsoft Graph service using Connect-MgGraph -Scopes "OrgSettings-AppsAndServices.ReadWrite.All".
2. Run the following Microsoft Graph PowerShell commands:

$uri = "https://graph.microsoft.com/beta/admin/appsAndServices"
$body = @{
    "Settings" = @{
        "isAppAndServicesTrialEnabled" = $false
        "isOfficeStoreEnabled" = $false
    }
} | ConvertTo-Json
Invoke-MgGraphRequest -Method PATCH -Uri $uri -Body $body

Related links

• Microsoft 365 admin center
• Manage add-ins in the Microsoft 365 admin center
• CIS Microsoft 365 Foundations Benchmark v7.0.0 - Page 59

Test Metadata

Field	Value
Test ID	CIS.M365.1.3.4
Severity	Medium
Suite	CIS
Product	Microsoft 365
Feature	Organization settings
Area	Applications and workload identities
Resource type	Tenant
User impact	Medium
Implementation cost	Low
MITRE ATT&CK	T1137.006 Add-ins
Supports benchmark	CIS Microsoft 365 Foundations Benchmark (version 7.0.0), requirement 1.3.4
Benchmark level	L1
Benchmark profiles	E3 Level 1, E5 Level 1
Supports controls	cis-m365:1.3.4, nist-800-53-r5:CM-7, nist-800-53-r5:CM-11
PowerShell test	Test-MtCisUserOwnedAppsRestricted
Services	Graph

Source

• Test: tests/cis/Test.CIS.M365.1.3.4.ps1
• Documentation: tests/cis/Test.CIS.M365.1.3.4.md