Detections
Analytics

1.2.2 Ensure that an exclusionary Geographic Access Policy is considered

Information

CAUTION: If these policies are created without first auditing and testing the result, misconfiguration can potentially lock out administrators or create undesired access issues.

Conditional Access Policies can be used to block access from geographic locations that are deemed out-of-scope for your organization or application. The scope and variables for this policy should be carefully examined and defined.

Rationale:

Conditional Access, when used as a deny list for the tenant or subscription, is able to prevent ingress or egress of traffic to countries that are outside of the scope of interest (e.g.: customers, suppliers) or jurisdiction of an organization. This is an effective way to prevent unnecessary and long-lasting exposure to international threats such as APTs.

Impact:

Azure AD Premium is required. Limiting access geographically will deny access to users that are traveling or working remotely in a different part of the world. A point-to-site or site to site tunnel such as a VPN is recommended to address exceptions to geographic access policies.

NOTE: Nessus has not performed this check. Please review the benchmark to ensure target compliance.

Solution

From Azure Portal
Part 1 of 2 - Create the policy and enable it in Report-only mode.

From Azure Home open the portal menu in the top left, and select Azure Active Directory.

Scroll down in the menu on the left, and select Security.

Select on the left side Conditional Access.

Click the + New policy button, then:

Under Assignments, select Users and Groups then:

Under Include, select All users

Under Exclude, only select emergency access accounts and service accounts (NOTE: Service accounts are excluded here because service accounts are non-interactive and cannot complete MFA)

Under Assignments, select Cloud apps or actions then:

Under Include, select All cloud apps

Leave Exclude blank unless you have a well defined exception

Under Conditions:

Select Include, then add entries for locations for those that should be blocked

Select Exclude, then add entries for those that should be allowed (IMPORTANT: Ensure that all Trusted Locations are in the Exclude list.)

Under Access Controls, select Grant and Confirm that Block Access is selected.

Set Enable policy to Report-only and click Create.

NOTE: The policy is not yet 'live,' since Report-only is being used to audit the effect of the policy.

Part 2 of 2 - Confirm that the policy is not blocking access that should be granted, then toggle to On.

With your policy now in report-only mode, return to the Azure Active Directory blade and click on Sign-ins.

Review the recent sign-in events - click an event then review the event details (specifically the Report-only tab) to ensure:

The sign-in event you're reviewing occurred after turning on the policy in report-only mode

The policy name from step 4 above is listed in the Policy Name column

The Result column for the new policy shows that the policy was Not applied (indicating the location origin was not blocked)

If the above conditions are present, navigate back to the policy name in Conditional Access and open it.

Toggle the policy from Report-only to On.

From PowerShell
First, set up the conditions objects values before updating an existing conditional access policy or before creating a new one. You may need to use additional PowerShell cmdlets to retrieve specific IDs such as the Get-AzureADMSNamedLocationPolicy which outputs the Location IDs for use with conditional access policies.

$conditions = New-Object -TypeName Microsoft.Open.MSGraph.Model.ConditionalAccessConditionSet

$conditions.Applications = New-Object -TypeName Microsoft.Open.MSGraph.Model.ConditionalAccessApplicationCondition
$conditions.Applications.IncludeApplications = <'All' | 'Office365' | 'app ID' | @('app ID 1', 'app ID 2', etc...>
$conditions.Applications.ExcludeApplications = <'Office365' | 'app ID' | @('app ID 1', 'app ID 2', etc...)>

$conditions.Users = New-Object -TypeName Microsoft.Open.MSGraph.Model.ConditionalAccessUserCondition
$conditions.Users.IncludeUsers = <'All' | 'None' | 'GuestsOrExternalUsers' | 'Specific User ID' | @('User ID 1', 'User ID 2', etc.)>
$conditions.Users.ExcludeUsers = <'GuestsOrExternalUsers' | 'Specific User ID' | @('User ID 1', 'User ID 2', etc.)>
$conditions.Users.IncludeGroups = <'group ID' | 'All' | @('Group ID 1', 'Group ID 2', etc...)>
$conditions.Users.ExcludeGroups = <'group ID' | @('Group ID 1', 'Group ID 2', etc...)>
$conditions.Users.IncludeRoles = <'Role ID' | 'All' | @('Role ID 1', 'Role ID 2', etc...)>
$conditions.Users.ExcludeRoles = <'Role ID' | @('Role ID 1', 'Role ID 2', etc...)>

$conditions.Locations = New-Object -TypeName Microsoft.Open.MSGraph.Model.ConditionalAccessLocationCondition
$conditions.Locations.IncludeLocations = <'Location ID' | @('Location ID 1', 'Location ID 2', etc...) >
$conditions.Locations.ExcludeLocations = <'AllTrusted' | 'Location ID' | @('Location ID 1', 'Location ID 2', etc...)>

$controls = New-Object -TypeName Microsoft.Open.MSGraph.Model.ConditionalAccessGrantControls
$controls._Operator = 'OR'
$controls.BuiltInControls = 'block'

Next, update the existing conditional access policy with the condition set options configured with the previous commands.

Set-AzureADMSConditionalAccessPolicy -PolicyId <policy ID> -Conditions $conditions -GrantControls $controls

To create a new conditional access policy that complies with this best practice, run the following commands after creating the condition set above

New-AzureADMSConditionalAccessPolicy -Name 'Policy Name' -State <enabled|disabled> -Conditions $conditions -GrantControls $controls

Default Value:

This policy does not exist by default.

See Also

https://workbench.cisecurity.org/files/4052

Item Details

References: CSCv7|12.1

Plugin: microsoft_azure

Control ID: 4d37533dbb55b5bb91935332734461acf1809a3c698a03754906a3f4921a5f94