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GLOSSARY

What is Two-factor authentication? (2FA)

DEFINITION

Two-factor authentication asks for a second proof of identity in addition to your password, usually a code from an authenticator app, a text message or a physical security key. Even if someone steals or guesses your password, they cannot log in without that second item.

Authenticator apps and security keys are stronger than text messages, which can be intercepted in some attacks. Save the backup codes when you set it up and keep them somewhere safe, because losing your phone without them can lock you out. Why it matters: It stops most account takeovers, which makes it the single most effective step to protect your site, email and ad accounts.

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