Multi-Factor Authentication: How It Improves Account Security

What Multi-Factor Authentication Is

Multi-factor authentication (MFA) requires proving your identity with more than just a password — typically a password (something you know) plus a second factor: a code from your phone, a physical security key, or a biometric scan (something you have or something you are). If an attacker obtains your password alone, through a breach, phishing, or guessing, MFA stops them from getting into the account without also possessing that second factor.

Why It Blocks Most Automated Attacks

Large-scale account takeover attempts are frequently automated — attackers test stolen or leaked username-password combinations against many services at once, a technique called credential stuffing. This approach relies entirely on the password being the only barrier. Microsoft and Google have both published data over the years indicating that enabling MFA blocks the overwhelming majority of these automated account compromise attempts, because the attacker's script has no way to supply the second factor.

Common MFA Methods

• SMS text codes — a one-time code sent by text message.
• Authenticator apps — a time-based code generated locally on your phone (Google Authenticator, Microsoft Authenticator, and similar apps), without needing a network connection.
• Push notifications — an approve/deny prompt sent to a trusted, already signed-in device.
• Physical security keys — a small hardware device (following standards like FIDO2/WebAuthn) you tap or insert to confirm sign-in.
• Passkeys — a newer, passwordless standard where your device itself proves identity using on-device biometrics or a PIN, tied cryptographically to the specific site.

Comparing the Methods

Authenticator apps and security keys are generally considered stronger than SMS, since text messages can be intercepted through carrier-level attacks (see below) and don't require compromising your phone number directly. Security keys and passkeys go a step further: they're designed to resist even real-time phishing, because the cryptographic proof they generate is tied to the actual website domain, so it simply won't work on a lookalike phishing page even if you're fooled into visiting one.

SIM Swapping and SMS Limitations

SIM swapping is a technique where an attacker convinces a mobile carrier to transfer your phone number to a SIM card they control, often using social engineering or stolen personal details. Once successful, SMS-based codes intended for you are delivered to the attacker instead. This is why security guidance has increasingly shifted toward recommending authenticator apps, security keys, or passkeys over SMS where a service offers the choice — SMS-based MFA is still far better than no MFA at all, but it's the weakest option among those listed above.

Where to Enable It First

Not every account needs the same priority. A sensible starting order is: your primary email account (since it's often used to reset passwords elsewhere), your password manager, financial and banking accounts, and any account tied to your identity or reused as a login method for other services (like a Google or Apple account used for "Sign in with" elsewhere). From there, extending MFA to remaining accounts as time allows continues to reduce overall risk.

Frequently Asked Questions