How to Prevent SIM Swapping: Why Biometric Authentication is the Better Way

8 October 2025

How to Prevent SIM Swapping: Why Biometric Authentication is the Better Way

8 October 2025

SIM swapping is one of the most common account takeover threats, and it’s surprisingly easy to pull off. With just a few pieces of personal information, fraudsters can convince mobile carriers to transfer your number to a new SIM card, giving them access to calls, texts, and most dangerously, your one-time passwords (OTPs).

The simplest and most effective way to prevent SIM swapping attacks is to stop using SMS for authentication. It’s outdated, insecure, and more costly than you think.

Here’s why, and how biometrics offer a safer, smarter alternative.

What is SIM Swapping?

SIM swapping (or SIM hijacking) happens when a criminal tricks or bribes a mobile carrier into moving your phone number to a SIM card they control. Once they have access, they can intercept SMS messages, including OTPs used for login, transaction approvals, and account recovery.

With access to your number, attackers can:

Reset your email or bank account passwords.
Bypass multi-factor authentication.
Lock you out of your accounts.
Steal money or sensitive information.

All of this without needing to have access to your FaceID, passwords, or PINs.

Why SMS OTPs Are a Security Liability

Despite being widely used, SMS OTPs are one of the least secure forms of authentication.

Here’s why:

1. Easily Intercepted

Whether through SIM swaps, phishing, or malware, SMS messages can be intercepted. And once an attacker has your OTP, they can log in as you, even if you have multi-factor authentication enabled.

2. No Identity Assurance

An OTP proves that someone has access to a phone, not that they are who they say they are. There’s no connection between the code and your actual identity. This makes SMS-based authentication inherently weak, especially for financial services and high-risk platforms.

3. High Operational Costs

Every SMS OTP comes at a cost. For large-scale platforms, this adds up quickly:

Telcos charge per message - rates vary by country, but they’re never free.
False positives and failed OTP deliveries increase support tickets.
Re-verifying users after SIM swap attacks often requires costly re-KYC.

Banks can spend tens of millions per year on SMS OTPs alone - only to remain vulnerable to fraud.

Biometrics: A More Secure Alternative

Biometric authentication solves the core problem with SMS OTPs: it checks the person, not just the device.

Instead of relying on something a user has (like a SIM card), biometric systems confirm who the user is by matching their face, fingerprint, or voice.

This makes SIM swap attacks irrelevant. Even if a criminal gains access to a phone, they still can't replicate a user’s biometric data.

But Not All Biometrics Are Secure: Why FaceID Isn’t Enough

Local biometric solutions like FaceID or Android Biometrics are a good start - but they come with serious limitations:

Anyone can re-register FaceID if they know the phone passcode. Once registered, that new face can access everything.
No link to the original account. Banks and apps can't tell if the biometric belongs to the person who originally signed up.
No cross-platform support. Local biometrics only work on the original device. If it’s lost or stolen, the user must re-enroll.

This makes FaceID-style systems vulnerable to family fraud, device theft, and credential manipulation - all of which can be just as damaging as SIM swap attacks.

Third-Party Biometrics: The Best Defence Against SIM Swapping

Third-party biometric solutions, particularly those using decentralized models, offer far stronger protection.

Here’s why:

1. Identity Assurance

Biometric authentication links a real person to their account. It’s not enough to have a phone—you have to be the person who originally enrolled into the account. This stops fraud dead in its tracks.

2. No Reliance on SMS or Passcodes

By removing SMSs from the authentication flow, third-party biometrics eliminate the risk of SIM swaps altogether. There are no codes to intercept, and no passwords to guess.

3. Seamless Across Devices

Advanced biometric systems like those using Zero-Knowledge Biometrics™ (ZKB) work across devices and platforms. Even if a user loses their phone, they can authenticate from a new one with just a selfie.

4. Privacy Preserving

Some centralized biometric systems raise privacy concerns. But decentralized solutions - like Keyless - use secure multi-party computation (sMPC) to match biometric data without ever storing or sharing it. No data is exposed, even if systems are compromised.

Real-World Benefits of Replacing SMS OTPs

Switching to biometric authentication doesn’t just improve security. It also reduces costs and improves the user experience:

Lower operational costs: No more SMS fees, support calls, or manual re-verification.
Stronger fraud prevention: Only real, verified users can log in or approve transactions.
Better UX: Users can authenticate in under 300ms with just a glance at their camera.

One fintech company replaced SMS OTPs with facial biometrics and saw a 40% drop in fraud and a 25% reduction in customer support tickets within the first six months.

The Bottom Line: It’s Time to Move Past SMS

SIM swap attacks are avoidable—but only if we stop using SMS OTPs as a crutch. While they’re easy to implement, they are no longer fit for purpose.

Biometric authentication, when done right, eliminates the need for codes and passwords altogether—making SIM swapping irrelevant and giving users back control of their identity.

But not all biometric systems are equal. Local options like FaceID leave too many gaps. Only third-party biometric solutions—especially those using privacy-preserving cryptography like ZKB—can provide the security, portability, and privacy needed to stay ahead of modern threats.

To find out how Keyless can help your organization prevent ATOs, improve UX, and protect your bottom line, schedule a personalised demo today.

How to Prevent SIM Swapping: Why Biometric Authentication is the Better Way

8 October 2025

How to Prevent SIM Swapping: Why Biometric Authentication is the Better Way

8 October 2025

What is SIM Swapping?

Why SMS OTPs Are a Security Liability

1. Easily Intercepted

2. No Identity Assurance

3. High Operational Costs

Biometrics: A More Secure Alternative

But Not All Biometrics Are Secure: Why FaceID Isn’t Enough

Third-Party Biometrics: The Best Defence Against SIM Swapping

1. Identity Assurance

2. No Reliance on SMS or Passcodes

3. Seamless Across Devices

4. Privacy Preserving

Real-World Benefits of Replacing SMS OTPs

The Bottom Line: It’s Time to Move Past SMS

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