Two-factor authentication (2FA) and multi-factor authentication (MFA) both add at least one additional step to the authentication flow by requiring more than one way to prove a user’s identity. The difference is subtle but important:
There’s a popular belief that more factors automatically mean more security. However, not all factors are created equal. One or two strong factors (such as a secure password) is often more secure (and less frustrating) than three weaker factors.
Below, we’ll dive into everything you need to know about 2FA and MFA, covering how authentication works, the difference between single-factor, two-factor, and multi-factor authentication, the various types of secondary authentication factors, the distinction between multi-factor and multi-step authentication, and how to secure your first factor before adding additional ones.
Authentication is the process of verifying a user’s identity. The most familiar approach is a username and password, which is a scalable, affordable, highly compatible, and privacy-friendly method that remains foundational in the vast majority of organizations. Around 95% of users in 2024 relied on passwords for authentication.
NIST (the National Institute of Standards and Technology) categorizes authentication factors into three broad categories:
When these are combined in various ways, you move from single-factor to two-factor to multi-factor authentication. Most organizations continue to rely on passwords as the essential first step, especially since they are easier to replace if compromised, do not rely on additional infrastructure, and don’t invade user privacy. In addition, even if an organization leverages biometrics as an authentication factor (“Something you are”), NIST requires that “An alternative non-biometric authentication option SHALL always be provided to the subscriber” because of the high rate of false rejections.
Therefore, the vast majority of organizations leveraging 2FA or MFA as defined by NIST 800-63B will be leveraging “Something you know”, most likely a password, somewhere in the authentication flow. Even when a username + password isn’t the primary authentication method, but rather an alternative or backup, it should still be secured in the same way as if it’s the primary authentication method.
Single-factor authentication (SFA) requires only one method to validate a claimed identity, most often a username and password. It’s the simplest setup, both for administrators to configure and for users to use and remember. Recent data from Microsoft shows that only about 22% of organizations’ users have MFA, meaning the vast majority use only passwords to secure their authentication. SFA can be secure so long as the password itself is strong and uncompromised
2FA requires users to prove their identity in exactly two ways. Typically, the first factor is a username and password (“something you know”). The second factor can either be something you have or something you are. When the first factor is secured properly
When the first factor is secured properly (e.g., by screening your users’ credentials against a continuously updated list of compromised passwords) 2FA provides another layer of authentication to support your defense-in-depth strategy.
Multi-factor authentication (MFA) requires at least two methods of identity validation. Because 2FA uses exactly two factors, all 2FA solutions are technically a form of MFA. However, MFA can also involve three or more factors by combining something you know, something you have, and something you are.
In most organizations, MFA effectively defaults to two factors, similar to 2FA, because adding more factors can be costly or overly complex for users. More is not necessarily better especially if those added factors are weak or repetitive. An additional factor should only be added once the first factor is secure.
All 2FA is technically MFA, but not all MFA is strictly 2FA. Realistically, most MFA implementations use only two factors. The question often becomes: “Which factors do I choose, and how do I ensure my base factor, a password, is secure?” Using a well-secured password as your starting point is key before considering additional factors.
It’s important not to confuse two-step or multi-step authentication with two-factor or multi-factor authentication:
Whether you opt for 2FA or MFA, the first factor, almost always a password, remains a constant in virtually all organizations. Because so many breaches begin with compromised credentials, it’s vital to secure that foundational password layer. Tools like Enzoic help organizations proactively detect weak or compromised passwords, protecting the first layer before adding any others. Only once the first layer is secure will additional layers meaningfully strengthen their defenses against unauthorized access and maintain a strong defense against the number one cause of a data breach.
AUTHOR
Josh Parsons
Josh is the Product Manager at Enzoic, where he leads the development and execution of strategies to bring innovative threat intelligence solutions to market. Outside of work, he can be found at the nearest bookstore or exploring the city’s local coffee scene.
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