What is a SIM swap attack?
- Author
- CRYPTO PORT Editorial
- Published
- Updated
- Reading time
- 4 min
In short
In a SIM swap, an attacker gets your mobile number moved onto a SIM they control, which hands them every code sent by SMS. Once the number is theirs, exchange logins and password resets fall one after another. The defence is to stop relying on SMS codes and to harden the identity checks your carrier performs.
Key points
- The attacker takes over the phone number itself
- SMS codes are the weakest form of two-factor authentication
- Move to an authenticator app or a security key
- Ask your carrier to add a PIN or port-out lock
Definition
A fraud in which someone impersonates you to your mobile carrier and has your number reissued onto a SIM they hold, so that every SMS code and voice verification reaches them instead of you.
Most services still treat a phone number as a recovery channel. An attacker gathers your name, birthday and address from social posts and old data leaks, then presents a plausible story to your carrier and asks for the line to be transferred. The moment it goes through, your handset drops off the network and the codes start arriving on theirs.
The damage compounds when the same number also protects your email. With the mailbox open, the attacker reads the reset links an exchange sends. Logging in, registering a new withdrawal address and re-enrolling two-factor authentication then fall in sequence, and the withdrawal is often complete before anyone notices.
The clearest warning sign is a phone that goes to no service and stays there for no reason you can explain. If coverage is normally fine where you are and the signal simply never returns, call your carrier from another line and, at the same time, ask your exchange to suspend withdrawals. Those two calls are what limits the loss.
Watch out for
- · Switch two-factor authentication on exchanges and your main email from SMS to an authenticator app or security key
- · Ask your carrier to add a PIN or port-out lock to the account so a transfer needs more than your personal details
- · If your phone loses service for no reason, call the carrier from another line and ask your exchange to freeze withdrawals