Two-factor authentication (2FA) is used to better protect both a user's credentials and the resources the user can access. It provides a higher level of security than authentication methods that depend on single-factor authentication (SFA), in which the user provides only one factor -- typically, a password or passcode. Two-factor authentication methods rely on a user providing a password as the first factor and a second, different factor.
For example, the CenturyLink password reset tool uses 2FA by sending a security code to a user's mobile device, which would be a possession factor. The password reset tool can also send a security code to a secondary email address. Because the user would need to know the password to the secondary email address to receive the security code, this would be a knowledge factor.
For instructions on how to reset a user's password use the related articles below: