Biometrics are NOT a good method of user verification.

 https://learn.microsoft.com/en-us/previous-versions/tn-archive/cc512578(v=technet.10)?redirectedfrom=MSDN

https://www.schneier.com/blog/archives/2005/04/security_risks_2.html

https://www.schneier.com/blog/archives/2009/01/biometrics.html

https://www.schneier.com/crypto-gram/archives/1998/0815.html#biometrics

From Schneier on security blog: 

"On the other hand, biometrics are easy to steal. You leave your fingerprints everywhere you touch, your iris scan everywhere you look. Regularly, hackers have copied the prints of officials from objects they’ve touched, and posted them on the Internet. We haven’t yet had an example of a large biometric database being hacked into, but the possibility is there. Biometrics are unique identifiers, but they’re not secrets.

And a stolen biometric can fool some systems. It can be as easy as cutting out a signature, pasting it onto a contract, and then faxing the page to someone. The person on the other end doesn’t know that the signature isn’t valid because he didn’t see it fixed onto the page. Remote logins by fingerprint fail in the same way. If there’s no way to verify the print came from an actual reader, not from a stored computer file, the system is much less secure.

A more secure system is to use a fingerprint to unlock your mobile phone or computer. Because there is a trusted path from the fingerprint reader to the stored fingerprint the system uses to compare, an attacker can’t inject a previously stored print as easily as he can cut and paste a signature. A photo on an ID card works the same way: the verifier can compare the face in front of him with the face on the card.

Fingerprints on ID cards are more problematic, because the attacker can try to fool the fingerprint reader. Researchers have made false fingers out of rubber or glycerin. Manufacturers have responded by building readers that also detect pores or a pulse.

The lesson is that biometrics work best if the system can verify that the biometric came from the person at the time of verification. The biometric identification system at the gates of the CIA headquarters works because there’s a guard with a large gun making sure no one is trying to fool the system.

Of course, not all systems need that level of security. At Counterpane, the security company I founded, we installed hand geometry readers at the access doors to the operations center. Hand geometry is a hard biometric to copy, and the system was closed and didn’t allow electronic forgeries. It worked very well.

One more problem with biometrics: they don’t fail well. Passwords can be changed, but if someone copies your thumbprint, you’re out of luck: you can’t update your thumb. Passwords can be backed up, but if you alter your thumbprint in an accident, you’re stuck. The failures don’t have to be this spectacular: a voiceprint reader might not recognize someone with a sore throat, or a fingerprint reader might fail outside in freezing weather. Biometric systems need to be analyzed in light of these possibilities.

Biometrics are easy, convenient, and when used properly, very secure; they’re just not a panacea. Understanding how they work and fail is critical to understanding when they improve security and when they don’t.

This essay originally appeared in the Guardian, and is an update of an essay I wrote in 1998."