Microsoft has added much-needed multi-factor authentication to its Windows Azure cloud computing platform, enabling organisations to secure access to any Azure services used by workers, partners and customers.

Available now, Active Authentication enables multi-factor authentication for Windows Azure Active Directory identities, the cloud-based service that provides identity and access capabilities for applications and other resources on Windows Azure itself.

Active Authentication requires users to authenticate themselves at sign in using an app on their mobile device or via an automated phone call or text message. This extra step helps prevent unauthorised access to data and applications in the cloud, Microsoft said.

The service is based on technology Microsoft gained from last year’s acquisition of PhoneFactor, a firm specialising in phone-based authentication.

Active Authentication can be used to secure access to Office 365, Windows Azure, Windows Intune, Dynamics CRM Online. There is also an Active Authentication SDK that customers can use to build multi-factor authentication into custom applications, Microsoft said.

Microsoft said that Azure customers can simply add the service to their Windows Azure AD tenant to enable it, after which users can enroll their own phone numbers and set authentication preferences during the standard sign in process.

Customers can choose to license Active Authentication based on a payment for each authentication, or on a per-user per-month basis.

The service is currently available as a preview, with pricing set at $1 per user per month, or $1 for every 10 authentications. Microsoft said it anticipated that pricing on general availability will be about double this amount. The firm declined to give a date for when it is expected to hit general availability.