Glossary / MFA (Multi-Factor Authentication)

MFA (Multi-Factor Authentication)

Authentication that requires two or more independent proofs of identity — something you know, have, or are — before granting access, rather than a password alone.

MFA factors fall into three categories: knowledge (a password or PIN), possession (a phone, a hardware security key), and inherence (a fingerprint or face scan). Requiring more than one means a stolen password alone isn't enough to get in — the attacker also needs the second factor.

Not all second factors carry equal weight. SMS one-time codes are widely supported but vulnerable to SIM-swap attacks; phishing-resistant factors like hardware security keys or passkeys (FIDO2/WebAuthn) are meaningfully stronger because they're cryptographically tied to the legitimate site and can't be phished by a fake login page the way a typed code can.

Push-based MFA introduced its own attack pattern — "MFA fatigue," where an attacker with a stolen password triggers repeated approval prompts until an annoyed user taps "approve" just to make them stop. Number-matching (the user has to enter a code shown on the login screen into the push prompt) closes that specific gap, which is why it's become the recommended default over a plain approve/deny push.

How Nexus handles this

Nexus applies the same "don't trust the connection alone, verify the request" logic MFA enforces at login to its own remote-management channel — every signed job is Ed25519-verified on the endpoint itself rather than trusted because it arrived over the right connection.

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