Multi-factor authentication (MFA) makes a stolen password less useful by requiring another, different kind of proof at sign-in. When a service offers them, passkeys or security keys are the strongest general choice against fake login pages; authenticator apps and push prompts add protection but can still be abused, while SMS is a useful fallback if it is the only option.
What is MFA?
MFA means proving your identity with at least two distinct authentication factors. The factors come from different categories:
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- Something you know: a password or PIN.
- Something you have: a security key, phone, or other registered device.
- Something you are: a fingerprint or face.
Two passwords do not count as MFA: both are knowledge factors. Some authenticators combine categories. As NIST explains in SP 800-63-4, Section 3.1.7, a multi-factor cryptographic authenticator is something you have and is activated by a factor representing something you know or something you are.
How does MFA protect an account?
If an attacker gets your password but not the other required factor, the attacker may be unable to complete the sign-in. MFA adds a hurdle; it does not guarantee that an account is safe. The protection depends on the method and the service’s sign-in flow. A service may remember a device or recognize it, so it may not ask for the second step every time.
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- POWERFUL SECURITY KEY: The Security Key C NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key C NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key C NFC via USB-C and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
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The method matters because some second steps can be tricked out of you. A code entered on a convincing fake sign-in page can be captured and used by an attacker. A passkey or security key uses a site-bound cryptographic response that helps prevent a fake site from capturing and replaying a valid sign-in response.
Which MFA method should I use?
Choose the strongest method the service supports, while making sure you can still recover access if you lose a device or key. Check the account’s security settings for labels such as passkey, security key, FIDO, or WebAuthn.
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- POWERFUL SECURITY KEY: The YubiKey 5C NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5C NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5C NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
- Use a passkey or security key when available. These use FIDO/WebAuthn. A security key is a separate hardware device; a passkey may be stored or used through a phone or computer’s built-in authenticator. The site-bound cryptographic exchange provides phishing resistance. Confirm that your account and devices support the option and understand the service’s recovery process.
- If FIDO is unavailable, use an authenticator app or a push option. A one-time code is an additional barrier, not a phishing-proof one: someone can trick you into entering it on a fake site. Push notifications can also be abused through repeated or unexpected approval requests. Approve only sign-ins you initiated and recognize. Number matching can help reduce accidental approvals, but it is not equivalent to FIDO phishing resistance.
- If SMS or voice is the only available second step, turn it on. It still adds a hurdle compared with password-only sign-in, but delivery through the phone network brings risks such as SIM changes and number porting. NIST advises services using the public telephone network to consider signals such as device swaps, SIM changes, and number porting.
For email, financial, work, and account-recovery accounts, check for a phishing-resistant option first. NIST highlights sensitive information and privileged users as situations where organizations should enforce or offer phishing-resistant authentication; the same prioritization is useful for personal accounts.
How do the common methods compare?
| Method | Phishing and replay resistance | Phone-number or network dependency | Device availability | Recovery consideration |
|---|---|---|---|---|
| Passkey or security key (FIDO/WebAuthn) | Phishing-resistant; site-bound cryptographic responses help prevent capture and replay at fake sites. | No phone number is inherently required. | May be a separate hardware key or built into a supported phone or computer. | Check the specific service’s recovery process and prepare for a lost device or key. |
| Authenticator-app code | Can be phished; NIST states OTP authentication is not phishing-resistant. | Does not inherently depend on SMS delivery or a phone number, though the app may be on a phone. | Requires access to the device with the authenticator. | Recovery depends on the service; check it before relying on a single device. |
| Push approval | Can be abused through unexpected approval requests; number matching reduces some accidental approvals but is not FIDO-equivalent. | Typically relies on a registered device and connectivity for prompts. | Requires the registered device and supported service flow. | Check the service’s recovery process if the device is lost or unavailable. |
| SMS or voice code | Can be phished; phone-network risks also apply. | Depends on access to the associated number and telephone service. | Requires access to the phone number, not necessarily an installed authenticator app. | Check how the service handles a lost number, SIM change, or number transfer. |
Recovery rules vary by service, so no single method guarantees easy account recovery. Before enabling a method, review the particular account’s recovery options and avoid relying on one device or key without a workable fallback.
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Is an authenticator app safer than SMS?
An authenticator app avoids relying on SMS delivery and the phone-number risks associated with number porting or SIM changes. But its one-time codes are still phishable: a fake sign-in page can capture a code. NIST SP 800-63-4, Section 3.1.4.1, states, “OTP authentication is not phishing-resistant.” So an app is generally preferable to SMS when those network risks matter, but neither offers the phishing resistance of FIDO/WebAuthn.
Are passkeys phishing-resistant?
Yes. FIDO passkeys and security keys used with WebAuthn are phishing-resistant because authentication is bound to the legitimate site rather than relying on a reusable code that can be typed into a lookalike page. NIST describes FIDO authenticators paired with the W3C Web Authentication API as a common, widely available phishing-resistant approach.
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- POWERFUL SECURITY KEY: The YubiKey 5 NFC is the most versatile physical passkey, protecting your digital life from phishing attacks. It ensures only you can access your accounts
- WORKS WITH 1000+ ACCOUNTS: Compatible with popular accounts like Google, Microsoft, and Apple. A single YubiKey 5 NFC secures 100+ of your favorite accounts, including email, password managers, and more
- FAST & CONVENIENT LOGIN: Plug in your YubiKey 5 NFC via USB and tap it, or tap it against your phone (NFC), to authenticate. No batteries, no internet connection, and no extra fees required
- MOST SECURE PASSKEY: Supports FIDO2/WebAuthn, FIDO U2F, Yubico OTP, OATH-TOTP/HOTP, Smart card (PIV), and OpenPGP. That means it’s versatile, working almost anywhere you need it
- PRIMARY & SPARE KEYS: Just like having a spare house key, we recommend buying two YubiKeys - one for daily use and one as a spare. That way you’ll never get locked out of your accounts
That protection is specific: phishing-resistant authentication helps address compromised or reused authenticators such as passwords and one-time passcodes. It does not stop every phishing objective, including attempts to install malware or collect personal information for another use.
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What MFA does not protect you from
MFA is one layer of account security, not a complete defense. It may block an attacker who has only your password, but it cannot ensure that every sign-in flow is safe or prevent all forms of device compromise, malware, or information theft.
Quick Recap
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- POWERFUL SECURITY KEY: The Security Key NFC is the essential physical passkey for protecting your digital life from phishing attacks. It ensures only you can access your accounts.
- WORKS WITH 1000+ ACCOUNTS: Compatible with Google, Microsoft, and Apple. A single Security Key NFC secures 100 of your favorite accounts, including email, password managers, and more.
- FAST & CONVENIENT LOGIN: Plug in your Security Key NFC via USB-A and tap it, or tap it against your phone (NFC) to authenticate. No batteries, no internet connection, and no extra fees required.
- TRUSTED PASSKEY TECHNOLOGY: Uses the latest passkey standards (FIDO2/WebAuthn & FIDO U2F) but does not support One-Time Passwords. For complex needs, check out the YubiKey 5 Series.
- BUILT TO LAST: Made from tough, waterproof, and crush-resistant materials. Manufactured in Sweden and programmed in the USA with the highest security standards.
- Keep your phone, computer, browser, and apps updated.
- Do not approve a push request you did not initiate, and do not share a sign-in code with someone who contacts you.
- Secure the email address and phone number used for account recovery, and review each service’s recovery settings.
- Use a passkey or security key for high-value accounts when supported; if it is not available, enable the strongest alternative offered.
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