Once the device is linked you'll have to enter the code from the Authenticator every time you log into the game or access your account settings on the WoW web page.

You must press the button on your Authenticator and enter the code it displays to complete your login. Can I apply my Blizzard Authenticator to more than one account? Yes!

This was announced last night, so we're sorry for missing it. Blizzard's announced the World of Warcraft Authenticator, "an electronic device that generates a six-digit security code at the press ...

The code will be required at every login to the account, whether at the game client or the official website. The Authenticator will go on sale for EUR 6 (GBP 4.75) at Blizzard's World Wide ...

Set to be debuted at the Worldwide Invitational, the Blizzard Authenticator is a small device which is associated with your WoW account. It generates a random six-digit code which must be entered ...