Is voice authentication still secure?

Voice authentication is not secure enough to rely on alone. It works by comparing the voice on the call with a stored voiceprint, and a good voice clone can match that voiceprint. University of Waterloo researchers reported an attack that bypasses voice authentication with up to a 99% success rate after six tries ¹, and they said the method can fool most voice authentication systems within six attempts ². The check still has a use, but only as one factor, never as the final approval.

Voice authentication checks a match, and a clone is built to match

Speaker verification asks whether a voice belongs to the person it claims to be. The IEEE describes it this way: the system accepts or rejects a claimed identity ³. The test is a comparison of sound, and a clone is designed to produce a sound that compares well.

That is why a system can be well built and still fail. The Waterloo result is about the method, not a careless bank. The researchers tested the attack against voice authentication systems, and their results describe what the attack can do, not a measured rate for any one bank. Read the 99% as proof that the approach can fail, not as the odds for your account.

A senior AI executive warns that some banks still accept voiceprints

Sam Altman, the chief executive of OpenAI, made the point in public in July 2025. At a Federal Reserve conference he said: "A thing that terrifies me is apparently there are still some financial institutions that will accept the voiceprint as authentication" ⁴. It is one executive's view, and the report does not name the institutions he meant. It does show that a senior AI executive has raised the concern in public.

Research on fake-speech detection shows the same problem. The ASVspoof 5 challenge summary reports that attacks significantly compromise its baseline systems, while the submitted systems brought substantial improvements ⁵.

It depends on the system, the attacker and what the check protects

The answer is not the same for every use:

• A low-stakes check is different from a payment. A voice check that only reads back a balance carries less risk than one that approves a transfer or changes a contact number.
• Extra factors change the odds. A check that combines voice with a one-time code sent to a device you already own is harder to pass with a clone alone. We did not find a published test of a specific bank's voice system, so the odds for your account are unknown.
• Voice data is sensitive. In Illinois, a voiceprint counts as a biometric identifier under the Biometric Information Privacy Act ⁶. Under the EU GDPR, biometric data is personal data from specific technical processing that allows or confirms a person's unique identification ⁷. These rules govern how a company collects and stores the data. They do not stop a clone from passing a call-center check.

What to use instead, and what to do now

Use a check that does not depend on how a voice sounds:

1. Treat voice ID as one factor. Never let it alone approve a payment or change the details on an account.
2. Call back on a number you already have. The FBI advises you to verify the identity of the person calling you or sending text or voice messages ⁸.
3. Ask whether a voice check is optional. If your bank offers a voice option, you can ask what else it checks before it approves a change.

For the scams that use voice clones to get past these checks, see our question on how to protect yourself from voice cloning scams. For the question of how much audio a clone needs, see the answer on that page. Our guide to voice cloning and deepfakes sets out the full picture, and the overview of voice privacy covers how voice data is kept.