Two-Factor Authentication for Beginners

Martin Shelton
8 min readJul 25, 2018
“A title card reading “two-factor authentication,” with an image of a login form, two-factor authentication codes on a phone, and a “sign in” button.

Passwords are the brittle wall that keep unwanted visitors out of your accounts. When it comes to account protection, two-factor authentication is one of the most effective defenses available.

Two-factor authentication (or 2FA, for short) strengthens login security by requiring a second piece of information — a second factor beyond your password. The second piece of information is usually a temporary code delivered by a device in your possession, such as your phone. It may also be something on your body, such as a fingerprint.

You might hear it referred to by a variety of names (e.g., multi-factor authentication, 2-step verification), but we’re going to stick with 2FA.

Why you should use 2FA

When large-scale password breaches happen — and they happen a lot — credentials are often sold and swapped in online marketplaces and hacking forums. Some attackers break into accounts for entertainment, and some, for a payday. It’s typically not personal. In rare circumstances, attackers have a specific group or person in their crosshairs.

Email accounts generally give attackers the most value. Why? You use your email to recover other web accounts.

Here are a few different ways your account is most likely to get hijacked.

These are common attacks that affect all email services. Enable 2FA everywhere you can, but especially on your email. Check if your favorite service supports it on Let’s walk through a few ways to use it.

2FA approaches

There are a few simple, widely supported approaches for adding 2FA to your accounts. There’s not one “right” way to use it, and each has unique considerations for security and convenience.

A pretty good option: SMS text messages
When setting up 2FA, most services allow you to use regular old text messages. When logging in, you will receive a short confirmation code on your mobile device. When prompted during login, enter your code.

2FA codes received through SMS text messages

Text messages are a painless way to access 2FA codes, but are only as reliable as the phone network. For example, if you lose network access or travel outside the country, you might not be able to receive the messages.

For most people, SMS-based 2FA is much better than using a password alone. But because telephone infrastructure itself comes with a great deal of baggage, SMS isn’t the most secure method available.

Here’s a great example. An attacker broke into the Twitter and email accounts of a prominent civil rights activist, Deray McKesson, by convincing Verizon to redirect his phone messages to a new SIM card on a remote device. This allowed the attacker to intercept his 2FA messages. If you own the phone number, you get the 2FA messages.

Screenshot of tweets from activist @deray, who describes having his phone number remotely stolen and SMS messages intercepted, allowing an attacker to hijack his Twitter account.

That sounds scary, but remember the real story here: The attacker was forced to work much harder than if they had simply entered a password.

It’s easy to prevent this kind of attack. Compared to SMS messages, authenticator apps are a little more convenient, and a lot more secure.

Better option: Authentication apps
Some services allow you to receive your temporary login code from a mobile app. There are many options to choose from, such as Google Authenticator, Authy, Duo Mobile, and others.

2FA codes received via the Google Authenticator app.

Some web services let you attach multiple authentication apps to the same account, which can be incredibly helpful for getting login codes when multiple people need access. Authenticator apps are also great because they work when you don’t have access to your phone network (e.g., when traveling internationally).

Unlike SMS messages, authenticator apps can’t be intercepted on the phone network, making apps a hardened option. When possible, consider an authenticator app over SMS.

But, just like passwords can be entered in a fraudulent website to steal your login information, authenticator codes can also be entered in a phony website. So we can do even better.

Best option: Security keys
Right now, security keys are one of the most secure and efficient ways to use 2FA. A security key is a physical USB device you can use to authenticate into your account.

They’re pretty inexpensive — one of the most popular options, a YubiKey, will run you $25.

When prompted to provide your 2FA credentials, instead of typing in a code, you simply insert your security key and physically tap it when prompted during login. That’s all. Security keys are fairly resistant to phishing attacks, making them one of the best options available. Unlike code-based 2FA, phishing sites don’t have a great way to intercept information from security keys.

The main problem with YubiKeys is that as soon as you try one, you’ll want to use them everywhere. And they can’t be used everywhere yet.

Security keys are not yet as well supported as authenticator apps, but the standard is getting traction on large websites. It can be used to log into Google, Facebook, Dropbox, and other services. Security keys are supported by most major browsers.

So just to recap, here are our three options:

Graph comparing two-factor authentication over SMS text messages, versus stronger authenticator app, versus still stronger security keys.

Use whichever 2FA method is available and practical for you. SMS-based 2FA is a worthwhile upgrade, but when possible, consider using authentication apps or security keys.

Let’s turn on 2FA!

We can set up 2FA in minutes. For example, let’s look at how to set it up for Gmail.

First, find the setup page.

Account icon (top right) > Manage your Google Account > Security > Signing in to Google > 2-Step Verification > Get started

Animation of user navigating to Google’s 2FA setup page

First, you must register the device. Punch in your phone number. You’ll be sent a confirmation code on your mobile device, which you will enter on the registration page. If you prefer not to use your phone number, we can always remove it later.

After registering your device, you can use 2FA codes through SMS text messages.

Authenticator app
For a more secure way to use 2FA, let’s activate the authenticator app.

First, go to the application marketplace of your choice and download an authenticator app, such as Google Authenticator, Authy, or Duo Mobile.

On the 2-step verification page, scroll down to “Authenticator app” and click “Set up.” To register a new service in the app, you will be asked to scan a barcode that appears on your screen. Scan the barcode with your phone’s camera. After the code appears in your app, type the code into the setup prompt.

If you have an authenticator app, there’s no need to use SMS text messages any more. (And like we said earlier, SMS 2FA comes with some risks we can easily avoid by only using an authenticator app.) Whenever possible, consider removing 2FA through SMS text messages after you set up an authenticator app.

Security keys
First, purchase a security key, such as a YubiKey. You can find one for $25.

A person tapping a Yubikey to activate it.

They’re easy to set up!

User navigating through Google’s security key registration interface.

Scroll down to “Security keys” and click “Add security key.” When prompted, insert the key into the USB port, and physically tap it.

Afterward, you can name your newly-registered device. During log in, instead of typing in a 2FA code, now you can just insert and tap the key.

If you already have authenticator apps or security keys set up, you probably don’t need SMS any more. If it’s not necessary, consider removing your phone number.

Scroll to “Voice or text message” and click the pencil icon, and then click “Remove phone.”

Some laptops (e.g., the Macbooks 2016 and beyond) only have USB Type-C ports. If you can’t use a traditional USB 2.0 or 3.0 port, you can still use security keys with a USB Type-C adapter. Here’s a short list of Type-C adapters that are confirmed to work.

It’s a little more expensive to purchase Type-C YubiKeys.

Whenever you can, use backup codes
Even if we lose our security key and authenticator app, we can still avoid locking ourselves out by using backup codes. Scroll down to “Backup codes” and click “set up.”

You will see a series of numeric codes. Print these out, because if you are ever locked out of your account, you will need one of these codes to get back in. Keep these codes someplace where you can physically access them.

A screenshot of Google’s 2FA backup codes

Get started!

Does your favorite service offer 2FA? Drop by to find out. If your service doesn’t yet offer 2FA, consider prodding the organization to support it.

Don’t stop here. Alongside turning on 2FA, strong password habits can go a long way to make your accounts safer. Want to learn more? Read about how to protect your accounts using password managers, for beginners.

This article is adapted from another article I wrote, Two Factor Authentication for Newsrooms, which originally appeared in Source. The most recent version can now be found at Freedom of the Press Foundation.



Martin Shelton

Writing about security for journalists, as well as beginners. Principal researcher at @freedomofpress.