Multifactor authentication (MFA) is a login control that asks for more than one proof of identity before granting access. Those proofs usually come from different categories: something you know, such as a password; something you have, such as a phone app or hardware token; or something you are, such as a fingerprint. By requiring a second factor, MFA makes stolen passwords far less useful on their own.
In cyber security, MFA is one of the strongest defenses against phishing, credential stuffing, and password reuse. Attackers often try to steal or buy credentials first, then use them to enter email, VPN, cloud, or payment systems. MFA can stop that first step, or at least force the attacker to bypass an additional control. It is especially important in environments that handle invoices, payments, and sensitive business records, where a single account takeover can lead to fraud, data theft, or extortion. MFA is most effective when combined with strong logging, least-privilege access, and protections against push fatigue and token theft.