Two Factor Authentication

Two Factor Authentication, also known as 2FA, 2 Factor Authentication, two step verification or TFA (as an acronym), is an extra layer of security that is known as "multi factor authentication." 

It requires not only a password and username but also something that only, and only, that user has on them (i.e. a piece of information only they should know or have immediately to hand - such as a physical token).

Tools

• Best way to protect yourself from hackers, scammers and snoops

• Two Factor Auth (2FA) - List of websites and whether or not they support 2FA.

Articles

• Two-Factor Authentication: Who Has It and How to Set It Up

• What is 2FA?

• Hackers Trying to Steal Your Tax Refund With Stolen SSNs

Also See

• Authenticator App by Google

• Multi-Factor Authentication

• Password Manager