Google has introduced a new two-step authentication feature for Gmail users that it says will significantly increase the security of the free mail service. The system enables users to set up a method for obtaining a secret code that will be required, along with a password, to access a Gmail account. Gmail, like virtually all other webmail services, has been a frequent target of attacks, both sophisticated and mundane, aimed at hijacking users accounts. Google will send that code to the user via SMS or a phone call.
Source: https://threatpost.com/google-adds-two-factor-verification-gmail-021011/74930/