Common Conditional Access policy: Block access for unknown or unsupported device platform

Users are blocked from accessing company resources when the device type is unknown or unsupported.

The device platform condition is based on user agent strings. Conditional Access policies using it should be used with another policy, like one requiring device compliance or app protection policies.

User exclusions

Conditional Access policies are powerful tools, we recommend excluding the following accounts from your policies:

• Emergency access or break-glass accounts to prevent tenant-wide account lockout. In the unlikely scenario all administrators are locked out of your tenant, your emergency-access administrative account can be used to log into the tenant to take steps to recover access.
  • More information can be found in the article, Manage emergency access accounts in Microsoft Entra ID.
• Service accounts and service principals, such as the Microsoft Entra Connect Sync Account. Service accounts are non-interactive accounts that aren't tied to any particular user. They're normally used by back-end services allowing programmatic access to applications, but are also used to sign in to systems for administrative purposes. Service accounts like these should be excluded since MFA can't be completed programmatically. Calls made by service principals won't be blocked by Conditional Access policies scoped to users. Use Conditional Access for workload identities to define policies targeting service principals.
  • If your organization has these accounts in use in scripts or code, consider replacing them with managed identities. As a temporary workaround, you can exclude these specific accounts from the baseline policy.

Template deployment

Organizations can choose to deploy this policy using the steps outlined below or using the Conditional Access templates.

Create a Conditional Access policy

1. Sign in to the Microsoft Entra admin center as at least a Conditional Access Administrator.
2. Browse to Protection > Conditional Access.
3. Select Create new policy.
4. Give your policy a name. We recommend that organizations create a meaningful standard for the names of their policies.
5. Under Assignments, select Users or workload identities.
   1. Under Include, select All users
   2. Under Exclude, select Users and groups and choose your organization's emergency access or break-glass accounts.
6. Under Target resources > Cloud apps > Include, select All cloud apps.
7. Under Conditions, select Device platforms
   1. Set Configure to Yes.
   2. Under Include, select Any device
   3. Under Exclude, select Android, iOS, Windows, and macOS.

      Note

      For the exclusion select any platforms that your organization knowingly uses, and leave the others unselected.

   4. Select, Done.
8. Under Access controls > Grant, select Block access, then select Select.
9. Confirm your settings and set Enable policy to Report-only.
10. Select Create to create to enable your policy.

After administrators confirm the settings using report-only mode, they can move the Enable policy toggle from Report-only to On.

Next steps

Conditional Access templates

Use report-only mode for Conditional Access to determine the results of new policy decisions.