Block

CA404-GuestUsers-AttackSurfaceReduction-SelectedApps-AnyPlatform-BLOCK

Block access

About this policy

The CA404-GuestUsers-AttackSurfaceReduction-SelectedApps-AnyPlatform-BLOCK policy blocks external users from the Microsoft admin portals. There is no everyday reason for a guest account to be anywhere near the Entra, Azure or Microsoft 365 admin centres, and attackers who compromise a guest identity will often probe exactly there. It applies to every guest and external user type across browser and client apps. It costs legitimate partners nothing and removes a route that should never have been open in the first place.

Policy conditions

Users: Specific users
Apps: Microsoft admin portals

JSON template

{
  "@odata.context": "https://graph.microsoft.com/beta/$metadata#identity/conditionalAccess/policies/$entity",
  "@odata.type": "#microsoft.graph.conditionalAccessPolicy",
  "@odata.id": "identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')",
  "@odata.editLink": "identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')",
  "templateId": null,
  "displayName": "CA404-GuestUsers-AttackSurfaceReduction-SelectedApps-AnyPlatform-BLOCK",
  "createdDateTime@odata.type": "#DateTimeOffset",
  "modifiedDateTime@odata.type": "#DateTimeOffset",
  "state@odata.type": "#microsoft.graph.conditionalAccessPolicyState",
  "state": "enabled",
  "deletedDateTime": null,
  "partialEnablementStrategy": null,
  "sessionControls": null,
  "conditions": {
    "@odata.type": "#microsoft.graph.conditionalAccessConditionSet",
    "userRiskLevels@odata.type": "#Collection(microsoft.graph.riskLevel)",
    "userRiskLevels": [],
    "signInRiskLevels@odata.type": "#Collection(microsoft.graph.riskLevel)",
    "signInRiskLevels": [],
    "clientAppTypes@odata.type": "#Collection(microsoft.graph.conditionalAccessClientApp)",
    "clientAppTypes": [
      "browser",
      "mobileAppsAndDesktopClients"
    ],
    "platforms": null,
    "locations": null,
    "times": null,
    "deviceStates": null,
    "devices": null,
    "clientApplications": null,
    "agents": null,
    "applications": {
      "@odata.type": "#microsoft.graph.conditionalAccessApplications",
      "includeApplications@odata.type": "#Collection(String)",
      "includeApplications": [
        "MicrosoftAdminPortals"
      ],
      "excludeApplications@odata.type": "#Collection(String)",
      "excludeApplications": [],
      "includeUserActions@odata.type": "#Collection(String)",
      "includeUserActions": [],
      "includeAuthenticationContextClassReferences@odata.type": "#Collection(String)",
      "includeAuthenticationContextClassReferences": [],
      "applicationFilter": null
    },
    "users": {
      "@odata.type": "#microsoft.graph.conditionalAccessUsers",
      "includeUsers@odata.type": "#Collection(String)",
      "includeUsers": [],
      "excludeUsers@odata.type": "#Collection(String)",
      "excludeUsers": [],
      "includeGroups@odata.type": "#Collection(String)",
      "includeGroups": [],
      "excludeGroups@odata.type": "#Collection(String)",
      "excludeGroups": [
        "2802b872-ccfb-4b29-a9a9-459808dfb11b",
        "86e8b29d-f7f2-4962-8a2d-65b8f0e5602f"
      ],
      "includeRoles@odata.type": "#Collection(String)",
      "includeRoles": [],
      "excludeRoles@odata.type": "#Collection(String)",
      "excludeRoles": [],
      "excludeGuestsOrExternalUsers": null,
      "includeGuestsOrExternalUsers": {
        "@odata.type": "#microsoft.graph.conditionalAccessGuestsOrExternalUsers",
        "guestOrExternalUserTypes@odata.type": "#microsoft.graph.conditionalAccessGuestOrExternalUserTypes",
        "guestOrExternalUserTypes": "internalGuest,b2bCollaborationGuest,b2bCollaborationMember,b2bDirectConnectUser,otherExternalUser,serviceProvider",
        "externalTenants": {
          "@odata.type": "#microsoft.graph.conditionalAccessAllExternalTenants",
          "membershipKind@odata.type": "#microsoft.graph.conditionalAccessExternalTenantsMembershipKind",
          "membershipKind": "all"
        }
      }
    }
  },
  "grantControls": {
    "@odata.type": "#microsoft.graph.conditionalAccessGrantControls",
    "operator": "OR",
    "builtInControls@odata.type": "#Collection(microsoft.graph.conditionalAccessGrantControl)",
    "builtInControls": [
      "block"
    ],
    "customAuthenticationFactors@odata.type": "#Collection(String)",
    "customAuthenticationFactors": [],
    "termsOfUse@odata.type": "#Collection(String)",
    "termsOfUse": [],
    "authenticationStrength@odata.context": "https://graph.microsoft.com/beta/$metadata#identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')/grantControls/authenticationStrength/$entity",
    "authenticationStrength@odata.associationLink": "https://graph.microsoft.com/beta/identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')/grantControls/authenticationStrength/$ref",
    "authenticationStrength@odata.navigationLink": "https://graph.microsoft.com/beta/identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')/grantControls/authenticationStrength",
    "authenticationStrength": null
  },
  "#microsoft.graph.restore": {
    "title": "microsoft.graph.restore",
    "target": "https://graph.microsoft.com/beta/identity/conditionalAccess/policies('c79d8d03-43da-435a-bbe0-4225f025d1c5')/microsoft.graph.restore"
  },
  "Tag": "jv-CAF-2026.2.1",
  "summary": "The CA404-GuestUsers-AttackSurfaceReduction-SelectedApps-AnyPlatform-BLOCK policy blocks external users from the Microsoft admin portals. There is no everyday reason for a guest account to be anywhere near the Entra, Azure or Microsoft 365 admin centres, and attackers who compromise a guest identity will often probe exactly there. It applies to every guest and external user type across browser and client apps. It costs legitimate partners nothing and removes a route that should never have been open in the first place."
}