Glossary
Authentication a fake site can't relay.
Phishing-resistant MFA is authentication that a fake website or man-in-the-middle cannot capture and replay, because the credential is cryptographically bound to the real site. FIDO2 passkeys and security keys are the common examples. SMS codes and authenticator-app codes are not phishing-resistant.
Field guide
Inventory every flow that sends a code, write the risk assessment NIST SP 800-63B-4 asks for, fix account recovery and new-payee setup first, then move customers to phishing-resistant or device-bound methods such as passkeys and in-app approval. Keep SMS only as a restricted fallback, with a dated plan to remove it.
Field guide
The durable fix is to remove the code the bot asks for, using passkeys, in-app approval on a registered device or network-based verification. While codes remain, say in every message what the code approves and that the bank will never ask for it, and treat a new-device sign-in during an inbound call as a strong fraud signal.
Field guide
Decide which passkeys you accept for which customers, offer enrollment right after a strong sign-in, make passkeys the default for returning users, and design account recovery that doesn’t fall back to an SMS code. Keep a non-SMS alternative for customers who can’t use passkeys, and a device-bound option for staff and other high-risk users.
Field guide
Map every authenticator you use to NIST’s assurance levels, identify the restricted ones (SMS and voice codes), and for each restricted authenticator document a risk assessment, user notice, a non-restricted alternative and a migration plan. Add a phishing-resistant option such as passkeys, which Revision 4 accepts at AAL2.
Buyer’s guide
Phishing-resistant MFA is authentication that a fake site or man-in-the-middle can’t capture and replay, because the credential is cryptographically bound to the real site. FIDO2 passkeys and hardware security keys are the common examples, and CISA also counts PKI-based smart cards. SMS codes, authenticator-app codes and simple push approvals are not phishing-resistant.
Buyer’s guide
There is no single best alternative for every flow. Passkeys are the most widely standardized phishing-resistant option and are accepted by NIST at AAL2. In-app approval on a registered device is what UAE and Singapore banks moved customers to. Carrier network checks are useful risk signals, and SIM-based cryptographic methods are emerging. Most organizations combine two or more.