Cis Azure Foundations 5.2.2

Ensure an exclusionary geographic Conditional Access policy is considered

Description

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.

Note on Assessment Status: Because the determination of entities to be included or excluded is specific and unique to each organization, assessment status for this recommendation is considered 'Manual' even though some elements for automation (CLI, PowerShell) are provided.

Impact

Microsoft Entra ID P1 or P2 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.

Audit Procedure

Using Azure Portal

1. From Azure Home open the Portal menu in the top left, and select Microsoft Entra ID.
2. Scroll down in the menu on the left, and select Security.
3. Select on the left side Conditional Access.
4. Select Policies.
5. Select the policy you wish to audit, then:
   • Under Assignments > Users, review the users and groups for the personnel the policy will apply to.
   • Under Assignments > Target resources, review the cloud apps or actions for the systems the policy will apply to.
   • Under Conditions > Locations, Review the Include locations for those that should be blocked.
   • Under Conditions > Locations, Review the Exclude locations for those that should be allowed (Note: locations set up in the previous recommendation for Trusted Location should be in the Exclude list.)
   • Under Access Controls > Grant - Confirm that Block access is selected.

Using Azure CLI

As of this writing there are no subcommands for Conditional Access Policies within the Azure CLI.

Using PowerShell

$conditionalAccessPolicies = Get-MgIdentityConditionalAccessPolicy

foreach($policy in $conditionalAccessPolicies) {$policy | Select-Object @{N='Policy ID'; E={$policy.id}}, @{N="Included Locations"; E={$policy.Conditions.Locations.IncludeLocations}}, @{N="Excluded Locations"; E={$policy.Conditions.Locations.ExcludeLocations}}, @{N="BuiltIn GrantControls"; E={$policy.GrantControls.BuiltInControls}}}

Make sure there is at least 1 row in the output of the above PowerShell command that contains Block under the BuiltIn GrantControls column and location IDs under the Included Locations and Excluded Locations columns. If not, a policy containing these options has not been created and is considered a finding.

Expected Result

At least one Conditional Access policy should exist with geographic location restrictions configured, blocking access from countries outside the organization's scope and excluding trusted locations.

Remediation

Remediate from Azure Portal

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

1. From Azure Home open the portal menu in the top left, and select Microsoft Entra ID.
2. Scroll down in the menu on the left, and select Security.
3. Select on the left side Conditional Access.
4. Select Policies.
5. Click the + New policy button, then:
6. Provide a name for the policy.
7. Under Assignments, select Users then:
   • Under Include, select All users.
   • Under Exclude, check Users and groups and only select emergency access accounts and service accounts (NOTE: Service accounts are excluded here because service accounts are non-interactive and cannot complete MFA).
8. Under Assignments, select Target resources then:
   • Under Include, select All cloud apps.
   • Leave Exclude blank unless you have a well defined exception.
9. Under Conditions, select Locations then:
   • 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.)
10. Under Access Controls, select Grant select Block Access.
11. Set Enable policy to Report-only.
12. Click Create.

Allow some time to pass to ensure the sign-in logs capture relevant conditional access events. These events will need to be reviewed to determine if additional considerations are necessary for your organization (e.g. legitimate locations are being blocked and investigation is needed for exception).

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.

1. With your policy now in report-only mode, return to the Microsoft Entra blade and click on Sign-in logs.
2. 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 6 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).
3. If the above conditions are present, navigate back to the policy name in Conditional Access and open it.
4. Toggle the policy from Report-only to On.
5. Click Save.

Remediate 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 such as the Get-MgIdentityConditionalAccessNamedLocation 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.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.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:

Update-MgIdentityConditionalAccessPolicy -PolicyId <policy ID> -Conditions $conditions -GrantControls $controls

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

New-MgIdentityConditionalAccessPolicy -Name "Policy Name" -State <enabled|disabled> -Conditions $conditions -GrantControls $controls

Default Value

This policy does not exist by default.

References

1. https://learn.microsoft.com/en-us/entra/identity/conditional-access/policy-block-by-location
2. https://learn.microsoft.com/en-us/entra/identity/conditional-access/concept-conditional-access-report-only
3. https://learn.microsoft.com/en-us/security/benchmark/azure/mcsb-identity-management#im-7-restrict-resource-access-based-on--conditions

CIS Controls

Profile

Level 2 | Manual