Why two-factor authentication is not foolproof but still good to use

A few days ago, I asked my followers on Twitter if they used the two-factor authentication on Twitter, or if they knew what two-factor authentication was in the first place. The result was that almost no one is using this. Most accounts that are hacked, are hacked because users are stupid and use terrible passwords, and they use the same passwords on every site where they have an account. This means that whenever some news site with terrible security is hacked, the hacker has access to more or less all these users’ accounts, including e-mail, social media and their favorite online stockbroker… This is admittedly bad.

Two-factor authentication comes to the rescue – using this, you cannot log in simply because you have the password and the username. You also need to have some third-party security token, like an app on your phone, a confirmation SMS sent to you, or a code generator device. If the hacker does not have access to this third-party token, he or she cannot take over your account. That is, at least, the design intent.

So, how can a hacker bypass the need for a third-party security token, or getting your leaked password in the first place? They can use a good old phishing attack. Set up a web page that looks like the one you want to log in to, trick you to go to the fake site and enter the login data, and then use these to access the real page. This process is illustrated below.

First, you need to trick the user to visit your fake login page, typically by sending some form of e-mail asking to log in and update something. The user submits username and password in the fake view, that you transfer to the real view in order to generate the third-party confirmation code. The real page, believing it is communicating directly with the legitimate user, sends the confirmation code to the user’s call phone. The user then submits this through your fake login view. Then you, as the hacker, will have access to the confirmation code, and you can take over the account. Depending on the type of site you can execute actions, or at least gain insight to the user’s personal data. For very poorly secured financial applications you can even steal the user’s money.

Of course, this is much more complicated to get to work than simply stealing a username and password, or brute-forcing a weak password, so 2-factor authentication makes a lot of sense. But like all barriers you put in place in risk management, it is not a magic pill solving all headaches. You still need to keep your guard up – don’t fall for phishing scams, don’t use the same password on multiple sites, use strong passwords and keep up to date on security features on the sites you are using and that are critical to you. Sites like Facebook and Google’s products can send you an e-mail or text you whenever there is a new login, with location and type of computer/browser. This is a very good extra layer of security.

To sum it up: use two-factor authentication, but also don’t forget to follow other common good security practices.

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