• Wed. Oct 11th, 2023

Two-factor Authentication and Ways to Bypass It

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ByWilliam Wilson

May 7, 2023
Two-factor authentication and how to bypass it
William Wilson
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Understanding the system`s vulnerabilities and knowing the hacker tricks can drastically enhance the account safety. This article will discuss 2FA types and hacker evading methods.

What is 2FA

2FA is an additional safeguard degree used with the traditional login method. The way it’s set up can differ based on the system’s needs or user choice. For heightened account security, MFA can be utilized, which includes multiple verification factors like a password, physical token, and biometrics. MFA is considered more secure than 2FA.

Different Types of 2FA

When it comes to 2FA, certain services and applications may provide the option to select the type of additional verification used alongside a password, while others may not. It’s important to explore all available options for 2FA.

SMS Method

To use this authentication method, users need to share the phone number and get a six-digit, one-time verification code via text message at each login, even on new devices. It’s a popular and convenient choice since SMS-enabled phones are common and no additional apps are required. However, network signal problems or phone performance issues can cause problems.

Voice Call Method

With 2FA via voice call, the user’s phone is called for authentication. In some applications, the call alone is enough to authorize entry, while others require the user to answer the call, listen to a six-digit code provided by a robot, and enter it into the required form.

Email Method

2FA by email functions similarly to 2FA by SMS, except that the one-time verification code is sent to the user’s email inbox. In some cases, email authentication may not require a code, but instead, a unique link is provided that grants access to the account. The disadvantages of this method are the amount of spam being sent to the mailbox and that it’s easy to hack. 

TOTP Authentication Apps Method

TOTP authentication uses a specialized software, for example Google Authenticator or Microsoft Authenticator on a user’s smartphone to generate a temporary, six to eight-digit code refreshed every half a minute. It provides more safety than 2FA by SMS as the code cannot be viewed on a lock screen or Bluetooth-linked device, and the smartphone must be unlocked or require a separate password for TOTP app access. A unique PIN for the TOTP authenticator makes it difficult to crack.

Hardware Key Method

The key involves using physical devices for authentication, such as a USB flash drive, NFC card, or TOTP key fob that generates a code every 30-60 seconds. This method is simple and highly secure, as it does not require an internet connection. However, it can be expensive for businesses to produce and maintain these devices for each user, and there is a risk of users losing them if they are required to carry them.

6 Methods to Evade Two-Factor Authentication

Although 2FA offers added security, each method has its own weaknesses. In the following section, we will discuss the methods that cyber attackers use to go through the two-factor authentication.

Social Engineering

In this attack, the person is tricked by the hacker to reveal the 2FA code. They first target the one’s login details and then contact them with a convincing story. Alternatively, the attacker may impersonate the victim and contact the service’s help desk. Successful social engineering can guarantee the attacker access to the victim’s account or change their password.

Open Authorization (OAuth)

OAuth lets apps and services obtain user data without revealing their password. Users give limited account authority to an app during login, so no password data is stored. In consent phishing, attackers pose as legitimate OAuth-enabled apps to request account access. They Evade two-factor authentication and login credentials if granted access.


Cybercriminals may utilize brute force attacks on outdated or poorly secured hardware, like TOTP key fobs with only four-digit codes. However, one-time codes created by these devices are brief (30/60 seconds), limiting attempts before expiry. Properly set two-factor authentication can lock out users after several incorrect OTP code attempts, making it hard for hackers to get access.

Pre-generated Tokens

Several platforms allow users to generate 2FA codes in advance, such as Google’s backup codes for lost authentication devices. However, if an attacker acquires the document or a single backup code, they can Evade 2FA and gain entry to the account.

Session Cookies

Session hijacking, or cookie theft, allows attackers to access user accounts without passwords or 2FA. Session cookies authenticate the account and track activity, which can be exploited until log out. Account hijacking can also occur through malware, cross-site scripting, and Evilginx for man-in-the-middle attacks. Evilginx captures login credentials and authentication codes through phishing links that redirect to a legitimate login page via a malicious proxy. Hijacked cookies Evade 2FA, even though one-time codes are not reusable.


This is a type of attack where the attacker takes control of the target’s phone number by pretending to be the user at a mobile operator’s store or through malicious apps. With control over the user’s phone number, the attacker can intercept SMS-based one-time codes for 2FA. Since SMS is a popular 2FA method, the attacker can access the victim’s important accounts and data one by one.

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William Wilson

With years of experience in the field, William curates captivating content and provides valuable insights on all aspects related to the Deep Lock. His in-depth understanding of the intricacies of the Darknet, cybersecurity, and digital privacy ensures that our readers receive accurate and up-to-date information.