SIM Swap Attack

A SIM swap attack is the takeover of a victim's phone number by persuading or bribing a mobile operator to move it to a SIM card the attacker controls. Once calls and texts arrive on the attacker's device, any account protected by SMS codes becomes reachable, including exchange logins, email and password resets. That chain is why SMS is the weakest common form of two-factor authentication for crypto accounts. It is also known as SIM hijacking or a port-out scam. Sensible mitigations include using an authenticator app or hardware security key instead of SMS, setting a port-out PIN or account lock with your carrier, and keeping the phone number used for financial accounts separate from the one published publicly.