After its acquisition by Microsoft, PhoneFactor became Windows Azure Multi-Factor Authentication.
PhoneFactor provides tokenless two-factor authentication using phones.
After you log in with your username and password, you receive a phone call to your pre-registered phone number asking you to confirm the login attempt. You press # to confirm the login, and you’re in. If a bad guy steals your username and password and tries to use them to log in, your phone will ring, so he won’t get in.
The product is available in both Enterprise and Web versions. The Enterprise version integrates into a range common enterprise environments, including Citrix, Microsoft Windows, RADIUS infrastructures, IIS-based websites, and more.
The Web edition is delivered in the form of an SDK in several programming languages, and can be used to add built-in support for PhoneFactor to your application.