Biometric systems have a powerful potential to provide security for a variety of applications, systems are nowadays being introduced in many applications and have already been deployed to protect personal computers, banking machines, credit cards, electronic transactions, airports, high security institutions like nuclear facilities, military bases and other applications like borders control, access control, sensitive data protection and on-line tracking systems. While biometrics may improve security in different environments and serve many purposes, biometric systems, like any other security system, have vulnerabilities and are susceptible to threats.