Allowing authentication only if several authentication factors are met meaning if 2 knowledge factors are used, then it is not MFA.
Authentication Factors
Knowledge
Information only the user should know
- SSN
- Username
- Password
- Birthday
Possession
Things that the user owns
- Smart Card
- Authentication Token
Inherence
Traits related to the identity of the user.
Location
Using GPS to authenticate based off if user is at home.
Temporal
Requiring logins at certain times of day or only within a certain window of time like 5 seconds.
Third Party Applications
Third party apps used for authentication into corporate services. They can issue temporary codes and act like Authentication Tokens.