Two-factor authentication (2FA) is method of access that requires two different forms of authentication.
In other words, you can enter the password, after which you will end up being prompted to enter an additional piece of information such as a security code. This security code will then be sent either to you through a mobile SMS, or through email. There is also phone verification, where your phone will be called and the code will be read to you by a voice assistant, or something similar. Essentially anything that requires more than just a simple password in order to provide you with access to a specific account can be considered two-factor authentication.
In other words, the first factor here is the password itself, while the second factor is a text with a code, or it can even be biometrics.
As for the biometric way of conducting two-factor authentication, you have three common options. For one, you scan your fingerprints, and since a lot of smartphones nowadays have a fingerprint sensor built-in, a lot of people tend to go with this route as it is quick and simple. The second is, of course, scanning your face. Most modern smartphones have 3D cameras that can scan your face efficiently from many angles, and this, in turn, allows for a higher level of security. In other words, someone cannot really open a picture of your face on their smartphone and manage to confirm that they are you, since it needs a full 3D model of your face in order to unlock. Last, you have one of the most complicated and rare kinds of biometric authentication, and this is through your retina.
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