It’s a technique offered by most major services, including Google and Facebook. Amazon and its Cloud Drive service are notable exceptions. Two-step verification typically works this way ...

Sites offering two-step verification — where you confirm that ... to print that out or write it down and keep it with you. Both Facebook and Twitter let other sites write apps that can connect ...

Two-step verification–also known as two-factor ... with a clever email or a Twitter or Facebook button labeled “Tell them to support 2FA.†Aside from entering your username and password ...

BTW, you can also protect accounts on Facebook, Twitter, LinkedIn, Paypal, Microsoft, Apple and lots of other sites with 2-step verification.