The Battle.net Mobile Authenticator, an application for mobile phones that provides an extra layer of account security, is now available as a free download for Windows® Phone 7 devices on the Windows Phone Marketplace. The Battle.net Mobile Authenticator provides a one-time password that you use in addition to your regular account name and password when you log in to a Battle.net account to play World of Warcraft or StarCraft II.
Versions for other mobile devices are also available for download here, or you can purchase a physical Battle.net Authenticator from the online Blizzard Store. Visit the Battle.net Mobile Authenticator FAQ for more information, or head to the setup page to get started after you've downloaded the application.
For additional account security advice, check out our Account Security page.