What are the warning signs of a SIM swap?

Your phone loses service for no reason. That is the whole warning, and the window is about an hour.

A SIM swap moves your phone number to somebody else's SIM, usually by convincing a carrier employee with information from a data breach. Your phone drops to no service, their phone starts receiving your codes.

If that happens with no explanation — no outage, no bill problem, no travel — treat it as a port-out until proven otherwise and call the carrier from another line immediately. Ask for the number back and for a port-out lock on the account.

What happens next if you do not: the email account is reset with an SMS code, and the exchange is reset from the email. That is the order, and it is why protecting only the exchange never works.

What prevents it: take the phone number off the recovery path for your email first, use an authenticator app or a hardware key, and add a carrier-level port-out PIN.

Account takeover has the full chain.

Last checked 19 Oct 2026.