What is 2FA (Two-Factor Authentication)? How it Works and Why it Matters?

Emails are now an integral part of daily communications. 

Every time you notice a message that your business email account has been accessed from an unidentified location—most likely—you quickly change your email password. However, the key question remains: How did attackers gain access to my email account in the first place?

There are multiple routes to access your professional email account, from phishing schemes, data breaches, and malware to weak passwords. The route taken to get authorized access determines how much of your information is stolen, and remember, even your strong password combination sometimes fails to protect against such breaches.

This is where two-factor authentication (2FA) comes in.

2FA adds an additional layer of security to your account. With 2FA, you can’t just submit your password and get access to your account. To authenticate access, you also need a unique verification identifier (an additional step) to get access to your account.

The use of two-factor authentication has significantly increased throughout email services, banking applications, social networking sites, cloud hosting services, and website control panels over the past few years. It’s one of the most effective and widely used methods of thwarting unauthorized access to online accounts.

In this guide, you’ll learn what 2FA is, how two-factor authentication works, what a 2FA code is, the different types of authentication methods available, how 2FA compares to MFA, and the best practices for securing your accounts.

TL;DR

What is 2FA?

2FA adds an additional layer of security by requiring two forms of verification when logging into an account, an app, or a system. The first form is typically something that is known, like a password or PIN, and the second form can either be something that you have, like a smartphone, an appropriately configured auth app, or a hardware security key. It can also be something that shows your unique identity, such as a fingerprint or a facial scan.

The purpose of two-factor authentication is to add another level of security to your account; once enabled, even if your password gets stolen or guessed, you still need the second form of verification to gain access.

The Three Authentication Factors

Most authentication systems rely on one or more of the following factor categories:

For example, when a person/breacher logs into an account with just the password, they are using a single method of authentication to gain access to that account. Compared to two-factor authentication, this method of access is less secure.

With two-factor authentication, the breacher needs a second method of authentication as well to gain access to any account. So even if they have obtained the username and password, it’s still difficult for the breacher to gain access to the account.

Step-by-Step: How does 2FA Works?

Two-factor authentication functions when you add another form of verification along with your PIN or password. This additional verification provides assurance for secure access to the account by the user only.

Here’s a detailed step-by-step guide on how a typical two-factor authentication process works:

Step 1: Enter username and password

Just like any other login process, you have to enter your username/email address/password on the website/application/service you want to log into. Here, the password serves as the first factor of authentication (i.e., information that you know).

Step 2: Server verification

Access will be denied if either of your username/password credentials does not match. Once it matches correctly, a second authentication factor is asked for instead of granting direct access right away.

Step 3: Second authentication factor prompt

After your password has been verified, a prompt for an additional authentication method (depending on what verification methods you have enabled) is sent: It includes:

• One-time password (OTP)
• Push notification request
• Hardware (USB) security key
• Fingerprint or facial recognition verification
• Other approved identification method

Step 4: Second authentication factor verification

Here, you put your second authentication factor for verification. This means that you need to validate your identity to gain access to your account.

Here are common examples of what the second authentication factor includes:

• A 6-digit verification code from the authenticator app
• SMS verification code sent to mobile device
• Approve button for your trusted devices
• A fingerprint or Face ID
• A security key to gain access

Step 5: Access granted

When the second authentication factor is validated, you are confirmed as the legitimate user and are permitted to access the account.

Thus, once both the first and second authentication factors are verified, the 2FA (Two-Factor Authentication) process is complete.

What is a 2FA Code?

A 2FA code is a temporary verification code used as the second authentication factor during the login phase of the 2FA process. After successfully entering your username/password, you need to input a second authentication code to prove your identity as the legitimate owner of the account.

Usually, a 2FA code is a short number (mostly, 6 digits). This code is valid only for a brief time (around 30-60 seconds). Because of the rapid cycling of numbers and inability to reuse them again (one-time use policy), these codes are more difficult for an attacker to exploit than a traditional password.

How Does a 2FA Code Work?

When you try to log in to an account with 2-factor authentication, the server first checks if your password is valid. In the next step, it generates a second authentication method in the form of a unique code.

This unique code only allows you to access your account.

If the code is entered correctly (within the valid timeframe), then you get access. However, if the code was incorrect (or expired), you have to create a new code and enter it again.

Where Do 2FA Codes Originate?

Where two-factor authentication codes are generated varies with the authentication type (e.g., texted to a user or voice call).

Why are 2FA Codes Important?

If your password is stolen or compromised, the breacher is unlikely to know your temporary verification code. The code is unique to each user and changes regularly, adding another barrier that makes unauthorized access more difficult.

Authentication codes help keep your online accounts, bank accounts, email accounts, cloud apps, and other devices with sensitive information safe. Familiarizing yourself with each type of 2FA helps you determine which is the best fit for your authentication needs and security level.

2FA Methods Comparison: What are the Types of 2FA Codes?

1. SMS/Voice One-Time Passwords (OTP)

The most popular form of 2FA is SMS and/or voice-based OTPs. When you attempt to log in, an automated message sends a temporary verification code to your registered mobile phone number through text message or automated voice call. You enter this code to complete the security authentication and log in to your account.

While 2FA via SMS OTP offers much greater security than simply relying on a user ID/password combination, security experts still recommend that you utilize a more secure alternative when available.

2. Authenticator Apps (TOTP)

Authenticator applications create time-limited one-time passwords (TOTP) on your device.

Applications such as Google Authenticator, Microsoft Authenticator, and Authy can create six-digit codes that automatically reset every thirty seconds. Since these codes are produced in real-time on your device, there is no need for them to use the SMS network or other forms of internet connectivity.

For most consumers, authenticator applications are among the most reliable ways to achieve the right balance between security and convenience.

3. Push Notifications

Push-based authentication directly mitigates the manual code authentication when you log into an application.

Here, at the time you try to log in, you receive a text message to a trusted device with an approval request. The device shows the login attempt, and you can choose to “approve” or “deny” the request.

Many identity service providers, including Microsoft Authenticator, Duo Security, and other enterprise-level identity solutions, use this method of authentication.

When push notifications are used correctly, users achieve an overall user experience and a high level of security.

4. Hardware Security Keys

Physical hardware security keys are used to provide authentication for users when they sign on to their account. A typical use case of a physical security key is connecting it (via USB, near field communication (NFC), or Bluetooth) to the authentication device and touching it at the time of authentication. Many modern security keys use FIDO2 or WebAuthn standards.

For people with critical accounts or who routinely handle sensitive data and documents, hardware security keys are one of the most trusted forms of two-factor authenticators.

5. Biometric Factors

Biometric authentication includes the use of fingerprint scans, facial recognition, iris recognition, or even voice recognition. Instead of having to enter a code number, users authenticate their identity by conducting a biometric scan with an approved device.

Biometrics are becoming increasingly common on mobile phones, laptop computers, and enterprise-level authentication systems.

What is the Best Type of 2-Factor Authentication (2FA)?

Generally speaking, when determining which 2FA method is best for you, authenticator apps (TOTP) typically provide the best balance between convenience, affordability, and security. If you have a highly sensitive account that needs added security, you may want to consider hardware security keys, which provide additional protection against phishing and credential-based attacks.

Whatever type of 2FA you decide to use, enabling these types of security measures will always provide a greater level of security than just using passwords.

2-Factor Authentication vs. Multi-Factor Authentication

2-factor authentication (2FA) and multi-factor authentication (MFA) are terms that are often used interchangeably; however, the terms are not synonymous.

The primary difference between the two types of authentication is based on the number of factors in the user’s authentication process.

2-factor authentication requires 2 separate authentication factors to verify the identity of the user, while multi-factor authentication is a general term to describe an authentication process that uses 2 or more distinct factors to authenticate the identity of the user. In summary, all instances of 2-factor authentication are examples of multi-factor authentication; however, not all examples of multi-factor authentication will be limited to just 2 authentication factors.

2FA is when an identity requires at least two separate pieces of information; for example, an account requires both a password and a one-time verification code sent to a user’s mobile device (SMS) to access the account and may utilize 2FA. However, if you added the requirement of a hardware security key and a fingerprint to log into your account, then the user is utilizing multi-factor authentication (MFA) because there are multiple pieces of independent criteria being requested to identify the user.

2FA vs MFA: Key Differences

What are the Benefits, Limitations & Threats of 2FA?

2FA is considered an effective means to improve the security of your online accounts; however, like any other means of securing sensitive data, 2FA through text messaging has advantages, disadvantages, and potential threats. A thorough review of the advantages and disadvantages allows the end-user to better protect their online account.

Benefits of 2FA

For most users, enabling two-factor authentication provides a substantial security improvement with minimal effort.

Limitations of 2FA

These limitations highlight why choosing the right type of 2FA is important, especially for accounts containing sensitive information.

Common Attacks Against 2FA

Although two-factor authentication provides high protection, cyber criminals continue to devise new ways to exploit weak examples of two-factor authentication.

• Phishing Attacks

As part of their advanced phishing schemes, cybercriminals can make fake login screens that capture both passwords and one-time (or temporary) verification codes. In cases where the victim has entered both their login credentials and OTPs on a fictitious site created by the cybercriminal before the temporary verification code times out, the cybercriminal can use the user credentials immediately.

• SIM-Swapping Attacks

A SIM-swapping attack occurs when a cybercriminal convinces the victim’s mobile carrier to transfer the victim’s phone number to a new SIM card that is under the control of the cybercriminal. Once the cybercriminal has completed this, the SMS-based authentication codes utilized for two-factor authentication are sent to the cybercriminal’s phone.

• MFA Fatigue (Push Bombing)

MFA fatigue, or push bombing, refers to an attack technique whereby an attacker attempts to convince the victim to authorize a login by sending repeated authentication requests to the victim’s devices. The repeated action forces the user until they agree to authorize at least one login attempt.

• Man-in-the-Middle Attacks

At times, an attacker can access and intercept communication in real-time between users and services. This allows the attacker to capture the user’s authentication information. Although modern encryption prevents this risk, poorly secured environments can still be vulnerable to this type of attack.

• Malware and Device Compromise

If malware installed by an attacker is infecting your device, this malware could potentially obtain your authentication codes, session tokens, or login credentials.

Best Practices for Using 2FA

Enabling two-factor authentication is an essential first step; however, how you implement and manage it affects your overall security. Below are several tested, successful methods that you can use to enforce the effectiveness of 2FA. Following these best practices maximizes the protection.

2FA Best Practices Quick Reference

• Activate 2FA for each account with critical information.
• The use of an authenticator app is preferred to SMS.
• Store backup / recovery codes in a safe place.
• Use a hardware security key to access high-sensitivity accounts.
• Ensure your recovery Information is up-to-date.
• Don’t approve unsought authentication requests.
• Generate strong, unique passwords in addition to 2FA.
• Regularly review your 2FA settings.

Knowing about best practices firmly establishes strong account security and offers max 2FA benefits.