Is SMS OTP secure?

SMS OTP, also known as a One Time Password, is a security measure that involves users receiving a unique code via text message to verify their identity during transactions or when logging into their accounts. While SMS OTP is commonly used for its convenience, it does have vulnerabilities that make it less secure compared to other authentication methods:

Phishing and Social Engineering

Attackers can employ phishing tactics to deceive users into disclosing their OTPs. They may send messages that appear legitimate requesting users to provide their OTPs for various reasons. Furthermore, social engineering techniques can be used to manipulate individuals into revealing their OTPs.

SIM Swapping

Cybercriminals can execute a swap by convincing a mobile carrier to transfer the victims phone number to a new SIM card under their control. This enables them to intercept SMS messages, including OTPs effectively bypassing the intended security measures.

Malware and Device Compromise

If a user’s device becomes compromised by malware, attackers can gain access to stored SMS messages on the device, including OTPs. This undermines the effectiveness of using OTPs for security purposes.

Network Vulnerabilities

Weaknesses in the network infrastructure can potentially lead to interception or redirection of SMS messages, particularly if outdated protocols are being used.

Lack of Forward Secrecy

SMS OTPs are not designed with forward secrecy in mind. If an attacker manages to obtain an OTP, they can potentially use it to access an account even after the user has changed their password.

As you can see, while SMS OTP offers convenience in verifying identities during transactions or account logins, it does have vulnerabilities that you should be aware of.

So what are the alternatives? The good news is that authentication solutions like Silent Authentication offer more protection while also reducing customer friction.

If SMS OTP is still your preferred (or only!) option, then you can protect yourself by running SIM Swap and other fraud checks prior to issuing the OTP. This adds protection by querying the Mobile Network Operator and detecting recent changes or settings that indicate fraud.