Not All MFA Is Equal: Moving to Phishing-Resistant Authentication

In brief: SMS and push-based MFA still stop bulk attacks, but modern phishing kits defeat them. Phishing-resistant factors like passkeys and hardware keys close the gap that one-time codes leave open.

MFA raised the bar — then attackers adapted

Multi-factor authentication dramatically reduced credential-stuffing success, and that win is real. But adversaries moved to real-time phishing proxies and MFA-fatigue attacks that harvest one-time codes or wear a user down with push prompts until they approve one.

The weakness is the shared secret: any factor a user can read and retype, an attacker can relay.

What phishing-resistant actually means

• Credentials bound to the origin, so a look-alike domain cannot relay them.
• Cryptographic proof of possession instead of a code the user copies.
• Passkeys and FIDO2 hardware keys as the strongest widely-available options.
• Push and SMS retained only as fallback, never as the sole factor for privileged access.

A pragmatic rollout

You do not have to boil the ocean. Start with the accounts that matter most — administrators, finance, and anyone who can approve changes — and require phishing-resistant factors there first. Expand coverage as enrollment tooling and device support catch up.

KENSAI's posture checks help you see where weak authentication still gates sensitive access, so the rollout targets real risk instead of guesswork.

Rolling it out without breaking users

Phishing-resistant methods such as passkeys and hardware security keys defeat the attacks that push notifications and one-time codes cannot, because there is no shared secret for a fake page to capture. The migration is as much about change management as technology.

Start with the highest-risk accounts, admins and anyone who can move money or data, then widen coverage in waves. Register a backup key for every user, define a vetted recovery path that is itself phishing-resistant, and measure adoption so the weak fallback methods can be switched off with confidence rather than guesswork.

Takeaway

MFA is necessary but no longer sufficient on its own. Phishing-resistant factors remove the relay-able secret, and rolling them out to high-privilege accounts first delivers the most risk reduction fastest.