Two-Factor Authentication (2FA) using OpenOTP

This guide is for security-aware individuals who wish to learn the theory behind user- based two-factor (or multifactor) authentication systems, also known as 2FA. Here we will discuss how 2FA systems work, and how to implement 2FA into a small, virtualized environment for testing purposes. By implementing 2FA, the hope is to enhance the cyber toolkit for administrators who wish to help mitigate the effects of user password theft by cyber intrusion. By following the steps outlined here, the reader should be able to comfortably configure a user account already existing in a Microsoft(R) Active Directory(R) (AD) environment to use the Google Authenticator application on his/her smartphone to authenticate with AD username and password+token for remote VPN access.