SIM Swap

A SIM swap is an attack in which a criminal takes control of your mobile phone number by convincing or bribing a telecom carrier to transfer it to a SIM card they control. Once they own the number, they receive your calls and SMS messages, including the one-time codes and password-reset links that many services send by text.

A typical attack against a crypto holder proceeds in stages: the attacker gathers personal details from data breaches or social media, impersonates the victim to carrier support claiming a lost phone, and gets the number moved. The victim's phone suddenly loses service, and within minutes the attacker resets the victim's email password via SMS, then uses the email and SMS codes to enter exchange accounts and withdraw funds. SIM swaps have driven some of the largest individual crypto thefts, and people who publicly signal large holdings are targeted deliberately.

The core defense is removing your phone number from the security chain: use authenticator apps or hardware security keys instead of SMS for two-factor authentication, and set a carrier PIN or port-freeze with your provider. A common misconception is that SIM swapping requires hacking your phone; the phone is never touched, because the weakness is the carrier's customer-service process, not your device. Self-custody wallets are unaffected directly, since they have no phone-number recovery.