Two-factor authentication is a method of identifying a user to enter the service, in which you ne to confirm in two different ways that he is the owner of the account. In some services, for example, “VKontakte”, it is call “entry confirmation. It is much more difficult for attackers who may ne your data for various reasons to gain access to your password, as well as a phone, email, or other authentication method at the same time. If only the password is us, the account remains vulnerable.
The following options for dual authentication
Passwords are easily leak to the Web, and not always Phone Number List through the fault of the user. How can you verify your identity? Most applications and services offer the user: Enter the code that the user receives in SMS or email after he has enter his login and password. This is the most common and easiest way, but it has its drawbacks: for example, SMS with a password can be intercept through a vulnerability in the protocol  through which they are transmitt. Enter the code that is generat in a separate authenticator application. Experts call this method more reliable  , besides, it remains available to the user, even if he does not have a mobile connection.
Which he can use if he does not have a mobile
To use it you must first install one of these applications (for example, Google Authenticator , Twilio Authy , Duo Mobile , Yandex. Key ), and then select the Buy Email List option of double authentication through the application in the menu of the desir service. A QR code will appear on the screen, which you will ne to scan through this application – and you can immiately use it. Many services (for example, VKontakte) also generate a number of backup codes for the user , connection or loses his phone. To do this, you ne to print out these codes in advance or save them in a safe place.