On the heels of the Syrian Electronic Army compromising a number of high-profile accounts—including those of the Associated Press, The Guardian, and The Onion—Twitter has introduced a two-factor authentication feature that should make such attacks more difficult. In a blog post today, Jim O'Leary of Twitter's security team announced the release of "login verification," an optional security measure that requires a verified phone number and e-mail address.
Twitter is a bit late to the two-factor authentication party. Word first spread that Twitter was working on a two-factor authentication scheme in February when the company advertised job openings for security engineers to develop "user-facing security features, such as multi-factor authentication and fraudulent login detection." Google has offered two-factor authentication since February of 2011, and Facebook introduced two-step login approval in May of 2011.
Like Google's two-factor authentication, Twitter's login verification sends a code via SMS to be entered to confirm login. But unlike Google's system, the code will be sent every time users sign in to Twitter through its website. This is the case even if it's from a computer or device that they've logged in from before. The phone has to be enrolled through Twitter's existing SMS service first—you have to text a code to Twitter to verify the phone first, which may not work with some phone carriers. The relationship between phones and accounts is also strictly one-to-one: if you have a shared business account, you're going to need to share a phone number too. If you have multiple accounts and only one phone number, you can only secure a single account.