# Multifactor Authentication (MFA)*

# Acronyms, Abbreviations, and Initialisms

# Glossary

Step-up authentication is an additional factor or procedure that validates a user's identity by using the following means:

• Challenge questions
• Out-of-band authentication (phone call or SMS)
• Dynamic knowledge-based authentication (questions unique to the end user)

# Overview

Authentication requires a match against a template or a known quantity. Therefore, variables (such as variable keystrokes) aren't useful for authentication.

Multifactor authentication requires at least two of the following:

• Type 1: Something you know
• Type 2: Something you have
• Type 3: Something you are

In some cases, a fourth factor is mentioned:

• Type 4: Something you do (linked to something you are); physiological and behavioral, such as how you write or type.

This field is constantly evolving, and additional considerations include:

• Time-based one-time passwords (TOTPs)
• Somewhere you are (location based)