Five authentication factors: 🔑 Something you
know, 📱 Something you
have, 👆 Something you
are, 📍 Somewhere you
are (location), 🎯 Something you
do (behavior/gait).
MFA requires factors from at least TWO different categories. SMS codes = something you have (weakest). FIDO2/WebAuthn hardware keys = strongest something-you-have.