Authentication Factor

An authentication factor is a piece of information used to authenticate or verify a person's identity for security purposes. Human authentication factors are generally classified into three cases:

Something the user has (e.g., ID card, security token, software token, phone, or cell phone)

Something the user knows (e.g., a password, pass phrase, or personal identification number (PIN))

Something the user is or does (e.g., fingerprint, retinal pattern, DNA sequence, signature, voice recognition, unique bio-electric signals, or another biometric identifier)

Often a combination of methods is used to provide multi-factor authentication. For example, bank machines provide two-factor authentication by requiring a bankcard and a PIN. Business networks may require users to provide a password and a random number from a security token.