What is two-factor authentication (2FA)?

Two-factor authentication (2FA) is a security process that enhances the protection of user accounts by requiring two distinct forms of identification before allowing access. This method combines something the user knows (such as a password) with something the user possesses (like a smartphone or a hardware token) or something inherent to the user (biometric data like fingerprints). The rationale behind 2FA is to add an additional layer of security; even if a password is compromised, unauthorized access can still be prevented by the requirement of the second form of identification.

This dual layer of protection makes it significantly more challenging for attackers to gain unauthorized access to accounts and information, as they would need to obtain both factors. This principle is widely recognized as a best practice in cybersecurity, especially for sensitive data and accounts.

The other options do not capture the essence of 2FA. For instance, a single password does not provide the added security that 2FA offers. Similarly, a backup authentication method typically refers to a recovery option rather than a primary security measure. Lastly, restricting access to one device does not address the two-factor requirement that defines 2FA. Therefore, the correct definition of two-factor authentication is indeed the process that requires two forms of identification.