Authentication : The verification of a person’s identity – Helps protect against unauthorized access.
Broken down into:
1. Something the user knows (password or PIN).
2. Something the user has (a smart card or other security token).
3. Something the user is (biometric reading: fingerprint or retina scan).
4. Something a user does (signature of voice print).
UAC (User Account Control) in Windows 7/Vista requires administrative login to perform higher tasks.
Source by wikipedia
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