Acknowledging that traditional passwords are no longer secure, some of the largest banks in the world are increasingly using voices, fingerprints, facial scans and other types of biometrics to safeguard bank accounts. Through their mobile phones, millions of banking customers routinely use fingerprints to log into their bank accounts. This feature, which some banks have introduced since the second decade of the 21st century, enables a huge share of banking customers to verify their identities with biometrics. The move reflects deep concerns that so many hundreds of millions of email addresses, phone numbers, social security numbers and other personal identifiers have fallen into the hands of criminals, rendering those identifiers increasingly ineffective at protecting accounts. "We believe the password is dying," said Tom Shaw, vice president for enterprise financial crimes management at USAA. "We realized we have to get away from personal identification information because of the growing number of data breaches." Long regarded as the stuff of science fiction, biometrics have been tested by big banks for decades, but have only recently become sufficiently accurate and cost effective to use on a large scale. It has taken a great deal of trial and error: With many of the early prototypes, a facial scan could be foiled by bad lighting, and voice recognition could be scuttled by background noise or laryngitis. Before smartphones became ubiquitous, there was another obstacle: To capture a finger image or scan an eyeball, a bank would have to pay to distribute the necessary technology to tens of millions of customers. A few tried, but their efforts were costly and short-lived. On top of all these, there is an even bigger problem: As criminals have found their ways to break the traditional banking passwords, they could eventually find ways to steal biometric data as well.