Definition
Two-factor authentication, or 2FA, is a security process that requires users to provide two different authentication factors to verify their identity. This typically involves something the user knows, like a password, combined with something the user has, such as a smartphone or a hardware token. When a user attempts to log in, they first enter their password, and then they are prompted for a second verification method, like a code sent to their phone. Implementing 2FA significantly enhances security by making it much harder for unauthorized individuals to gain access even if they compromise one authentication factor. For instance, logging into your bank account often requires both your password and a one-time code sent via text message. This is distinct from multi-factor authentication (MFA), which requires at least two factors but may involve more than two. You will encounter 2FA concepts on exams like CompTIA Security+, CySA+, and CISSP.