SIM swap scam: signs, what to do first and how to protect your number

Many accounts use your phone number to send a code when you sign in or reset a password. A criminal who controls the number can receive those codes, reset your email and empty a bank or crypto account in minutes. The attack does not need your phone. It needs your carrier to move the number. Knowing the signs, and having a plan, can be the difference between a bad day and a big loss. This guide covers both, and how to make your number harder to take.

How a SIM swap scam works

Signs you may have been SIM swapped

• Sudden No Service or SOS only while Wi-Fi still works and nearby phones have bars.
• A text or email from your carrier about a SIM change, an eSIM activation or a number transfer you did not ask for.
• Calls and texts stop arriving, or your friends tell you they got odd messages from you.
• Password reset or login alerts you did not request, from email, banks or social apps.
• You are locked out of accounts because the code is going to someone else's phone.

A single dropped signal is usually not a swap. Towers fail, and a damaged SIM can cause No Service. The warning sign is a loss of service that lasts, together with alerts about account changes. If both appear, treat it as a swap until you know otherwise. If your phone only has no signal, see why a Samsung says not registered on network for non-fraud causes.

What to do right away if you think you were SIM swapped

How to protect your number from a SIM swap

• Add a PIN or passcode to your carrier account that is not your birth date or phone number. Ask for one if you do not have it.
• Turn on your carrier's number lock. Verizon, AT&T and T-Mobile each offer a feature that blocks SIM changes or number transfers unless you turn it off first. Look in your account security settings.
• Use an authenticator app or a security key instead of text codes, wherever the service allows it. Passkeys are stronger still.
• Do not share codes. No bank or carrier will ask you to read out a verification code.
• Keep personal details private. Do not post your birth date, address or phone number publicly.
• Use unique, strong passwords from a password manager, so one breach does not open every account.

Your number transfer PIN is also a key. Keep it private, and read how the number transfer PIN works so you know when a carrier should and should not ask for it.

Why text codes are the weak link

Text message codes are better than no second step, but they travel over the phone network and depend on the carrier's checks. An authenticator app keeps the code on your device, so moving your number does not move your codes. Hardware security keys and passkeys go further and cannot be handed over to someone on the phone. Switch your email, bank and password manager first, because those are the accounts that unlock the others. Keep backup codes in a safe place, so you do not lock yourself out when you change phones.

SIM swap, port-out fraud and phishing: what is the difference?

• SIM swap: the number is moved to a new SIM on the same carrier.
• Port-out fraud: the number is moved to a different carrier, using an account number and a transfer PIN.
• Phishing: a message tricks you into giving up a password or a code. It often comes first, and sets up the swap.

Defenses overlap. A number lock helps with both swaps and port-outs, and an authenticator app helps no matter how the thief gets in. Phishing messages are often the first step, so learn the signs of a scam text.

Does an eSIM or a new phone change the risk?

An eSIM cannot be pulled out of a stolen phone, which helps if your phone is lost. But the number can still be moved to another eSIM or SIM if a carrier is tricked, so the protection comes from the account PIN and number lock, not the type of SIM. If you are moving to a new phone, make the change yourself in the carrier app, and note any unexpected SIM or eSIM activation emails. See eSIM explained.

What your carrier can do for you

Carriers can lock your account so that SIM changes and number transfers need extra steps, and they can flag your line for extra checks. Ask for a note on the account that says no changes without a PIN and photo ID in a store. They can also review recent SIM changes, find out how the swap was done and help with your police report. Keep the names and case numbers of the people you talk to. If the carrier is slow to help, ask for a supervisor, and say the words SIM swap fraud, which usually moves a case to a specialist team.

Who gets targeted, and why?

Anyone with a phone number can be a target, but criminals pick people with something to take: bank and investment accounts, crypto, a business or a large social media account. They also go after people whose details leaked in a data breach, because that gives them a head start in passing the carrier's checks. Posting your birth date, address or pet names publicly helps them guess security answers. You do not need to be rich to be hit, since a stolen email account can be used to reset many other things. That is why the basic steps matter for everyone.

Check your accounts for a recovery phone number that is not yours, and for forwarding rules in your email that you did not set up. Thieves sometimes add both so they keep access after you regain your number. In Gmail, look under Settings › See all settings › Forwarding. In Apple Account, check Sign-In and Security for trusted phone numbers.

If money was taken

Contact the bank, the exchange or the payment service right away, and say the loss came from a SIM swap. Banks have a short window to dispute some transfers, and records are easier to get early. Ask for a written case number, save your carrier's records of the SIM change and add the details to your police report. Keep a log of every call, with the date, the name and what was said. These help with disputes, insurance and any investigation.