SMS authentication is a user verification method that identifies users using a code that is delivered to them through an SMS message on their cell phone. It is also known as two-factor authentication (2FA) as it is mostly used as a second verifier for users to acquire access to an application, system, or network.

SMS authentication is employed by most application developers but it is not considered a strong security method. In this article, you will learn why SMS authentication is considered an insecure technique by discussing its different pros and cons. But first, let's get started with the basic concept of SMS authentication and how does it works.

SMS Authentication: How does it work?

SMS authentication is very easy to use. When a user signs into his account, an empty text box will appear on the screen requiring a code that is sent on your mobile device via a text message within a few seconds.

You need to enter that SMS authentication code in the empty box to gain access to the application or website you are signing into such as Gmail, Facebook, Twitter, etc.

This authentication technique provides an extra security layer. In such scenarios, an attacker would need to steal your mobile device and user password in order to access your account illegitimately.

Advantages and Disadvantages of SMS Authentication

SMS authentication has several advantages and disadvantages, which we have discussed as follows:


  • Additional layer of security: SMS authentication offers more security than passwords alone as they can be stolen/guessed easily by the hacker, or can be forgotten by the user himself.

  • Convenient Technique: Many users give the same passwords for their multiple accounts to avoid remembering different ones for each account. SMS authentication relieves users from this trouble by sending a unique code on their device for identity verification.

  • Better than no 2FA: Securing your system or application with a 2FA technique is better and safer than no 2FA at all. It will increase the satisfaction level of your users.


Though, SMS authentication has many uses, it has some disadvantages as well, including:

  • SIM Swapping: The unauthorized users can gain access to your account by transferring the legitimate user's number to their phone after contacting the company and providing the stolen data of the legitimate user like SSN. This is called SIM swapping.

  • SIM Hacking: Nowadays, SIM hacking is very easy and common. For example, malicious attackers can manipulate the cell tower and entire SS7 system to gain the confidential data of the users.

  • Lost and Synced Devices: Many devices are lost on a daily basis which can be extremely risky as the attackers can take private information from them. It becomes riskier when the devices are signed into various social media accounts, making it easier for attackers to misuse legitimate users' data.

  • Social engineering attacks: These are the attacks where malicious users act as the original user or organization to convince the targets to hand over all important information including passwords and SMS codes to acquire unauthorized access.

  • Cost: SMS authentication is quite expensive to implement, depending on the service providers and the number of SMS messages transmitted.

Is SMS Authentication Secure or Insecure?

Considering the advanced attacking techniques emerging on daily basis, SMS authentication is not a very secure method. In 2016, the National Institute of Standards and Technology (NIST) stated to prevent the use of SMS authentication as it is a vulnerable technique.

The SMS-based 2FA technique is still popular due to its easy deployment and user-friendly approach, especially for beginners. Moreover, everyone is now used to this security method while logging into their account either for funds transfer, email access, or playing games, as they find it a quick and seamless authentication scheme.

Alternative Methods

SMS-based authentication is better than implementing no authentication technique at all. But, there are some alternative methods as well for businesses to make their systems more secure.

FIDO2 (WebAuthn)

FIDO2 is a security technique based on public key cryptography that is used to deal with phishing attacks. In 2019, the World Wide Web (WWW) announced it as the new web standard for password-less logins. FDIO2 examples include on-device authentication such as Windows Hello on Windows 10, Finger-lock on Android, and TouchID on MacBook.

Mobile Authentication Apps

Mobile Authenticator Apps perform just like SMS authentication. When a user logs into his account or website, either the authenticator app will send an OTP on your device or a push notification that requires you to approve or disapprove the login request. These codes expire after a few minutes, making them more secure than the SMS-based techniques.

Going Beyond SMS Authentication

The technology is advancing rapidly, and so are the attacking techniques which are becoming more complex to detect and prevent from breaching into the systems and acquiring confidential data.

Therefore, the organizations and businesses must go beyond passwords and codes, and choose such security techniques that detect malicious activity as soon as it occurs in any part of the system or network, and remove it instantly.