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Security Fundamentals & Crypto · Foundational

Knowledge Factor

Authentication factor based on something the user knows, such as a password, PIN, or passphrase.

Definition

Knowledge factors are the most common and the weakest because they can be guessed, phished, reused, or stolen. Security questions are a weak knowledge factor since answers are often discoverable. NIST SP 800-63B discourages knowledge-based authentication for identity verification.

Example

A six-digit PIN used to unlock a Windows Hello key is a knowledge factor tied to the device.

Exam tip

PINs and passwords are both knowledge factors; combining them is not MFA.

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