http://us.battle.net/d3/en/forum/topic/5592454673?page=9#176
"While no security method is 100% fool-proof (even Authenticators), please note that it is possible that players reporting to have been compromised while an Authenticator was attached to their Battle.net account may have been using the Dial-in Authenticator. The Dial-in Authenticator does not provide the same level of protection as the Battle.net Authenticator or Battle.net Mobile Authenticator app, and -- more importantly -- is not currently supported for Diablo III."
Post made by Community Manager.