Anyone who's paid attention to computer security over the past few years will probably tell you that your password isn't enough. Passwords are often awkward and hard to remember--leading people to use the same password for multiple sites--and if someone gets a hold of your login credentials, they can wreak havoc with your personal information. Not good.
Using two-factor authentication can't prevent all security headaches, but it can keep your accounts a good deal safer.
What is two-factor authentication, anyway?
Two-factor authentication adds another step to the login process when you sign in to a website or app. You enter your username and password as you normally would, but instead of being logged in, you will then be asked to enter in a security code that expires after a single use. In a sense, it's a password for your password.
There are multuple ways to get these security codes: The most common is via a simple text message to your phone, and most services that offer two-factor authentication default to this option. Depending on the service, you can also get codes through specialized smartphone apps, via email, or through specialized "security token" devices--dedicated pocket-sized devices that can generate and provide security codes for you.
Not without its headaches
Everything comes with compromises, and added security is no exception. Two-factor authentication has its fair share quirks and idiosyncrasies.
For services like Gmail and Twitter that work with third-party client apps, you may need to generate app-specific passwords for use with apps that don't support two-factor authentication. It's generally easy to generate these app-specific passwords, but it's another step that stands between you and your account.
There's also the issue of what to do if you ever lose your phone or authentication token. Most services have ways to log in case you lose your phone or token, often using security questions, a backup login key that you need to write down and keep in a safe place, or a message sent to a secondary point of contact, such as an email address.
How to set it up
Here's how to turn it on for six popular online services.