All terms
A second proof of identity beyond your password.
Two factor authentication adds something you have to something you know. The strength varies enormously: hardware keys are excellent, authenticator apps are good, SMS is weak.
Every exchange account should have it enabled, and it should not be SMS if any alternative exists.
A YubiKey or similar hardware key is the strongest option and defeats both phishing and SIM swaps.
That SMS two factor is good enough. A phone number can be taken over by a SIM swap, which defeats it entirely, and that attack is common precisely because so many people rely on text codes. An authenticator app or a hardware key is a different class of protection.
Common questions
Which type of two factor authentication should I use?
What happens if I lose my authenticator?
Where this comes up on the site
The guides that actually use this word, rather than a list of everything we have written.
Where to go next
More security terms
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