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Consider an exclusionary Geographic Access Policy (Manual)​

Profile Applicability​

• Level 1

Description​

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

You can use Conditional Access Policies to block access from geographic locations 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.

Audit​

From Azure Portal​

  1. From Azure Home open the Portal menu in the top left, and select Azure Active Directory.
  2. Scroll down in the menu on the left, and select Security.
  3. Select on the left side Conditional Access.
  4. Select the policy you wish to audit, then:
    • Under Assignments, Review the Users and Groups for the personnel the policy will apply to
    • Under Assignments, Review the Cloud apps or actions for the systems the policy will apply to
    • Under Conditions, Review the Include locations for those that should be blocked
    • Under Conditions, 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.

From Azure CLI​

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

From Azure PowerShell​

$conditionalAccessPolicies = Get-AzureADMSConditionalAccessPolicy 

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.

Remediation​

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 Azure Active Directory.
  2. Scroll down in the menu on the left, and select Security.
  3. Select on the left side Conditional Access.
  4. Click the + New policy button, then:
  5. Provide a name for the policy.
  6. Under Assignments, select Users or workload identities then:
    • Under Include, select All users
    • Under Exclude, select Users and groups and only select emergency access accounts and service accounts (NOTE: Service accounts are absent here because service accounts are non-interactive and cannot complete Multi-Factor Authentication (MFA))
  7. Under Assignments, select Cloud apps or actions then:
    • Under Include, select All cloud apps
    • Leave Exclude blank unless you have a well defined exception
  8. Under Conditions, select Locations then:
    • Select Include, then add entries for locations for those to block
    • Select Exclude, then add entries for those to allow (IMPORTANT: Ensure that all Trusted Locations are in the Exclude list.)
  9. Under Access Controls, select Grant and select Block Access.
  10. Set Enable policy to Report-only.
  11. Click Create.

NOTE: The policy is not yet 'live,' since Report-only is auditing the effect of the policy.

Part 2 of 2 - Confirm that the policy is not blocking expected access, then toggle to On:

  1. With your policy now in report-only mode, return to the Azure Active Directory blade and click 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 are reviewing occurred after turning on the policy in report-only mode
    • You can see the policy name from Part 1 Step 5 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 preceding 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.

From Azure 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 preceding condition set:

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

References​

https://docs.microsoft.com/en-us/azure/active-directory/conditional-access/howto-conditional-access-policy-location
https://docs.microsoft.com/en-us/azure/active-directory/conditional-access/concept-conditional-access-report-only
https://docs.microsoft.com/en-us/security/benchmark/azure/security-controls-v3-identity-management#im-7-restrict-resource-access-based-on--conditions

Additional Information​

Test these policies by using the What If tool in the References. Setting these can create issues with logging in for users until they use an MFA device linked to their accounts. You can perform further testing via the insights and reporting resource in References which monitors Azure sign ins.

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