What Is Two-Factor Authentication (2FA)?

Two-factor authentication (2FA) is a security system that requires two distinct forms of identification in order to access something.

Two-factor authentication can be used to strengthen the security of an online account, a smartphone, or even a door. 2FA does this by requiring two types of information from the user—a password or personal identification number (PIN), a code sent to the user's smartphone, or a fingerprint—before whatever is being secured can be accessed.

Key Takeaways

  • Two-factor authentication (2FA) is a security system that requires two separate, distinct forms of identification in order to access something.
  • The first factor is a password and the second commonly includes a text with a code sent to your smartphone, or biometrics using your fingerprint, face, or retina.
  • While 2FA does improve security, it is not foolproof.

Understanding Two-Factor Authentication (2FA)

Two-factor authentication is designed to prevent unauthorized users from gaining access to an account with nothing more than a stolen password. Users may be at greater risk of compromised passwords than they realize, particularly if they use the same password on more than one website. Downloading software and clicking on links in emails can also expose an individual to password theft. 

Two-factor authentication is a combination of two of the following:

  • Something you know (your password)
  • Something you have (such as a text with a code sent to your smartphone or other device, or a smartphone authenticator app)
  • Something you are (biometrics using your fingerprint, face, or retina)

2FA is not just applied to online contexts. It is also at work when a consumer is required to enter their zip code before using their credit card at a gas pump or when a user is required to enter an authentication code from an RSA SecurID key fob to log in remotely to an employer’s system.

Despite the slight inconvenience of a longer log-in process, security experts recommend enabling 2FA wherever possible: email accounts, password managers, social media applications, cloud storage services, financial services, and more.

Example of Two-Factor Authentication (2FA)

Apple account holders can use 2FA to ensure that accounts can only be accessed from trusted devices. If a user tries to log in to their iCloud account from a different computer, the user will need the password, but also a multi-digit code that Apple will send to one of the user's devices, such as their iPhone.

Special Considerations

While 2FA does improve security, it is not foolproof. Hackers who acquire the authentication factors can still gain unauthorized access to accounts. Common ways to do so include phishing attacks, account recovery procedures, and malware.

Hackers can also intercept text messages used in 2FA. Critics argue that text messages are not a true form of 2FA since they are not something the user already has but rather something the user is sent, and the sending process is vulnerable. Instead, the critics argue that this process should be called two-step verification. Some companies, such as Google, use this term.

Still, even two-step verification is more secure than password protection alone. Even stronger is multi-factor authentication, which requires more than two factors before account access will be granted.