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Defensive Security Cybersecurity Glossary

Multi-Factor Authentication (MFA)

A security mechanism requiring two or more forms of verification before granting access.

Full Definition

Multi-Factor Authentication (MFA) is a security mechanism that requires users to provide two or more verification factors to gain access to an account or system. The three authentication factor categories are: something you know (password), something you have (hardware token, authenticator app), and something you are (biometrics).\n\nMFA significantly raises the cost of credential-based attacks — even if a threat actor obtains a user's password through a breach or phishing, they cannot log in without the second factor. However, MFA is not impenetrable: SIM swapping, MFA fatigue attacks (push notification spam), adversary-in-the-middle (AiTM) phishing, and session cookie theft can all bypass certain MFA implementations.\n\nInfostealers that capture active session cookies effectively bypass MFA entirely, as the session is already authenticated. This highlights the importance of session management and short session lifetimes alongside MFA enforcement.

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