SIM Swap Attacks & Why SMS 2FA Isn’t Enough

SIM swapping is one of the fastest-growing account takeover methods. Here’s how it works, why SMS 2FA is vulnerable, and what to do instead.
SIM Swap Attacks & Why SMS 2FA Isn’t Enough

📱 SIM Swap Attacks & Why SMS 2FA Isn’t Enough

Two-factor authentication (2FA) is essential for account security — but not all 2FA is created equal.
SMS-based 2FA, while better than nothing, is increasingly vulnerable to SIM swap attacks, a method criminals use to hijack your phone number and intercept your authentication codes.

This guide explains how SIM swaps work, why SMS is risky, and the safer alternatives you should use.

🕵️‍♂️ What Is a SIM Swap Attack?

A SIM swap (also called SIM hijacking or SIM jacking) happens when an attacker convinces your mobile carrier to transfer your phone number to a SIM card they control.

Once they have your number, they can:

  • Receive your calls and text messages
  • Intercept one-time passcodes sent via SMS
  • Reset passwords for email, bank, crypto wallets, and more

⚠️ Why SMS 2FA Is Vulnerable

SMS 2FA depends on your phone number, not your device. That means:

  1. If someone takes over your number, they get your 2FA codes.
  2. Attackers can use social engineering to trick carrier reps.
  3. In some cases, attackers bribe or compromise carrier employees.

Real-world attacks:
High-profile crypto thefts and social media account takeovers have been traced to SIM swaps, with victims losing millions — sometimes in minutes.

🔑 Stronger Alternatives to SMS 2FA

Instead of SMS, use:

  • App-based TOTP codes (Google Authenticator, Authy, Proton Authenticator)
  • Hardware security keys (YubiKey, SoloKey, Titan)
  • Passkeys (phishing-resistant and don’t depend on your phone number)

Proton Authenticator is worth calling out — it’s free, open-source, works on iOS, Android, Windows, macOS, and Linux, and offers encrypted sync. Ideal for replacing SMS 2FA without adding complexity.

🛡️ How to Reduce Your SIM Swap Risk

  1. Add a carrier PIN or passphrase to your account — required before making changes.
  2. Opt out of remote SIM swaps if your carrier allows.
  3. Don’t reuse your phone number as a recovery method for all accounts.
  4. Audit your recovery options — replace SMS recovery with email or app-based options where possible.
  5. Watch for sudden service loss — your phone losing signal unexpectedly can mean your number’s been ported.

📌 When You Must Use SMS 2FA

Some services still only offer SMS codes. If that’s the case:

  • Pair it with strong, unique passwords from a password manager.
  • Enable account alerts so you get notified of logins or changes.
  • Keep a hardware or app-based backup for other accounts so SMS isn’t your only second factor.

🗣️ Final Word

SMS 2FA is better than no 2FA — but it’s not bulletproof.
If your accounts matter to you (and they do), switch to app-based or hardware 2FA wherever possible.

And remember: your phone number is an identity key in today’s online world. Protect it like you would your bank PIN.