SIM swap
A SIM swap is an attack where a scammer moves your phone number onto their own SIM card. They then receive your SMS codes and use them to break into your email, bank and crypto exchange.
How it works
The attacker gathers your details from data leaks and social media, then convinces your mobile carrier that they are you and lost their SIM. Sometimes a bribed employee helps. The carrier issues a new SIM, your phone loses signal, and your calls and texts go to the scammer.
Next they hit "forgot password" on your email, exchange and messengers and get the reset codes by SMS. If login is protected only by a password and SMS, they now have full access. Funds can leave an exchange within minutes.
Crypto holders are a favourite target because transfers cannot be reversed. Defence is about making your phone number stop being the key to everything: an authenticator app or hardware key instead of SMS, a separate number for important accounts, and a carrier lock on SIM changes without an in-person visit where your carrier offers one.
One evening your phone suddenly shows "No service". Twenty minutes later you get emails about a password change on your exchange, and ten minutes after that about a 0.15 BTC withdrawal. The scammer had your texts the whole time. With an authenticator app and an address whitelist, SMS alone would not have been enough.
The main mistake is leaving SMS as the only second factor on exchanges and email, and tying your number to the recovery of everything. Switch to an authenticator app or hardware key, turn on a withdrawal whitelist, and keep your phone number off social media. If your phone loses service out of nowhere, call your carrier from another phone right away.
Questions and answers
What is a SIM swap in simple terms?
It is theft of your phone number: a scammer gets a new SIM issued in your name and starts receiving your SMS codes.
How do I know if I have been SIM swapped?
Usually your phone suddenly loses service even though coverage is fine around you. Emails about password changes or new-device logins may arrive at the same time.
How do I protect myself from SIM swaps?
Do not use SMS as your second factor anywhere money is involved; use an authenticator app or hardware key. Ask your carrier whether you can block SIM changes without an in-person visit.
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Updated: 2026-10-19