Offer Ends In
00
:
00
:
00
:
00
SMS One‑Time Passwords (OTPs) are temporary passwords delivered to users via Short Message Service (SMSto confirm their identity and that no one else is using the account. They are sent to a user’s mobile device often during a login attempt or sensitive transaction.
OTPs often replace or complement traditional passwords, adding a layer of security or speeding up the login process, as they make unauthorized logins much harder than with passwords, which if stolen, keep the user account vulnerable.
OTPs are generally safe, and they are widely adopted by businesses worldwide, including fintech and banking applications, which are among the most sensitive. However OTPs don’t come with zero risk, and in this article, we are sharing the most common vulnerabilities of OTPs so that you ensure your platform delivers more options or uses OTP from a vendor that minimizes vulnerabilities.
SMS‑based authentication is highly susceptible to phishing and smishing attacks, where attackers create fake messages, calls or pages that mimic the ones delivered by the original app or the trusted source, tricking users into entering or saying their authentic OTP codes which are directly received by the attackers.
Attack tools that help fraudsters with this have become increasingly sophisticated, intercepting credentials and codes in real time via fake web pages or phone scams that can trick users to think they are customer service representatives, leading users to hand over their authentication codes.
SIM swap fraud remains one of the most critical risks of SMS OTP security. In this type of attack, the attacker uses social engineering tricks and approaches a mobile carrier, making them transfer the victim’s phone number to a SIM card the attacker owns.
This can be both through tricking an employee, or them actually doing it intentionally in exchange of something. When the attacker has the number, they also have the SMS OTPs and can access all the victim’s accounts.
The Signaling System No. 7 (SS7) protocol, which is the backbone of global cellular communication, lacks mandatory authentication or encryption for SMS routing. This makes SMS messaging come with clear vulnerabilities that sophisticated attackers can exploit to redirect or intercept sensitive messages like OTP messages.
The message can be intercepted in their way, making it unnecessary for the attacker to compromise the user’s device. These flaws, being on the level of the infrastructure, are hard to fix.
Man‑in‑the‑Middle (MitM) Attacks and Session Hijacking
Attackers may employ man‑in‑the‑middle techniques that sit between the user and the legitimate service, capturing both credentials and OTPs as they are entered during a login session. Such attacks can also take place through Wi‑Fi networks or compromising browser sessions, giving attackers full session control like they have accessed the account while the user remains unaware.
Mobile carriers periodically recycle inactive phone numbers, which can result in a new subscriber receiving OTPs intended for the previous number owner. If users do not update account contact details or are unaware, this can lead to unintended access to sensitive authentication codes by random people.
Authentica’s developer-friendly API enables OTP verification via SMS with the maximum level of security to eliminate whatever vulnerabilities that can be eliminated.
With no development effort, and with the easiest possible integration and a pay-as-you-go model to pay only on-demand, you can use OTP without going through the journey from scratch. This also allows you to comply with standards, get to the market faster and reduce initial costs drastically.
SMS‑based OTPs represent a great evolution from traditional passwords to a more secure form of dynamic authentication that adds a layer of protection from unauthorized access. However, SMS OTPs still have a list of vulnerabilities, which we have discussed here. Some of these vulnerabilities are at the level of the infrastructure and can't be solved just easily.
Being an essential form of authentication for most apps due to its accessibility and ease of use, you need to make sure that you have selected the most secure provider for SMS OTP like Authentica.
