SIM Swap Fraud: How Thieves Hijack Your Phone Number and Access Your Bank Accounts

SIM swap fraud is a growing cybersecurity threat that allows criminals to take control of your phone number, intercept banking verification codes, and potentially steal money from your accounts. Learn how this scam works, the warning signs to watch for, and how a carrier PIN and other security measures can help protect your identity and finances.

Your phone number is more important to your financial security than you might think. Many banks, financial institutions, and online services use mobile numbers to verify identities, send login codes, and approve password resets. Unfortunately, criminals have found ways to exploit this system through a scam known as SIM swap fraud.

SIM swap fraud happens when a criminal convinces a mobile carrier to transfer someone else's phone number to a SIM card or device they control. Once the transfer is complete, the victim may suddenly lose mobile service while the criminal starts receiving their calls and text messages.

This can become particularly dangerous when banks send one-time passwords (OTPs) through SMS. If criminals intercept these verification codes, they may be able to access financial accounts, reset passwords, and carry out unauthorized transactions.

The good news is that wireless carriers offer security features that can make these attacks more difficult. Setting up an account PIN, enabling a number lock, and using authentication apps instead of SMS verification can significantly improve your protection.

Here's how SIM swap scams work, how to recognize the warning signs, and what you can do to protect your phone number and financial accounts.

How Do Criminals Hijack a Phone Number Without Accessing Your Phone?

SIM swapping is a type of identity theft in which criminals transfer a victim's existing phone number to a SIM card under their control.

To carry out this scam, a fraudster typically contacts the victim's wireless carrier and pretends to be the legitimate account holder. They may use stolen personal information, leaked passwords, or other identifying details to convince customer support that they own the account.

Once the carrier approves the request, the victim's phone number is transferred to the criminal's SIM card.

Another related technique is called port-out fraud. Instead of transferring the number to a different SIM on the same network, criminals request that another wireless carrier transfer the victim's number to its service.

Both methods can give criminals control over incoming calls and text messages.

This creates a serious security problem because many financial institutions still rely on SMS verification to confirm account access.

The Federal Communications Commission (FCC) has warned that SIM swapping can allow criminals to intercept text messages and phone calls used to authenticate financial, social media, and other accounts. Attackers may then change login credentials, obtain sensitive information, or drain bank accounts.

Consumer complaints also highlight the financial consequences of these attacks. Reports submitted to the Consumer Financial Protection Bureau (CFPB) describe account takeovers, fraudulent transactions, weak identity verification, and inadequate responses from companies.

Federal Rules Require Wireless Carriers to Verify Customers' Identities

To reduce SIM swap fraud and unauthorized number transfers, the FCC introduced new security requirements for wireless service providers.

The commission adopted these rules in a Report and Order released on November 16, 2023.

Under the requirements, wireless carriers must take additional steps to protect customers before processing SIM change and port-out requests.

Important protections include:

• Identity verification: Carriers must use secure methods to confirm a customer's identity before approving a SIM change.

• Immediate notifications: Customers must receive notifications about SIM change requests before the requested changes take place.

• Account locking options: Wireless providers must offer customers the ability to lock or freeze their accounts against unauthorized SIM changes at no additional cost.

• Port-out protection: Similar identity verification, notification, and account-locking requirements apply when customers transfer their numbers to another carrier.

• Recordkeeping: Providers must maintain records of SIM change requests for at least three years.

These requirements give customers additional opportunities to identify suspicious activity and prevent criminals from taking control of their phone numbers.

However, customers should still activate the available security features rather than relying entirely on their carrier's standard protections.

Who Can Set Up a Carrier PIN, and What Does It Protect?

A carrier account PIN is one of the simplest ways to make unauthorized changes to a mobile account more difficult.

Most major wireless providers offer account security options such as PINs, passcodes, SIM protection, or number locks.

These features help prevent someone from making important account changes without providing the required verification information.

For example, a number lock can prevent unauthorized transfers of your mobile number to another SIM card or wireless provider.

The important thing to understand is that a carrier PIN protects your wireless account, not every other account connected to your phone number.

Your bank account, email address, investment accounts, and credit information require separate security measures.

Additionally, a PIN cannot completely protect you if criminals already have your passwords or manage to trick you into sharing a verification code.

For stronger protection, combine your carrier's security features with additional authentication methods.

5 Important Ways to Protect Yourself From SIM Swap Fraud

Protecting your phone number requires more than simply using a strong mobile password. You should secure your wireless account and reduce your dependence on text-message verification.

Here are five practical steps that can help.

1. Set Up a Strong Mobile Carrier PIN

Contact your wireless provider and ask how to create an account PIN or passcode.

Choose a unique combination that criminals cannot easily guess. Avoid using birthdays, simple number sequences, or the same PIN you use for banking services.

If your carrier offers a separate SIM protection or number lock feature, consider enabling it as well.

These additional safeguards can make it harder for someone to transfer your phone number without authorization.

2. Use an Authenticator App Instead of SMS Codes

SMS verification is convenient, but it can become vulnerable when criminals take control of your mobile number.

An authenticator app offers another layer of protection. These applications generate temporary verification codes directly on your device rather than sending them through text messages.

Some banks, brokerages, email providers, and other online services support authenticator applications or physical security keys.

Where available, consider using these methods instead of relying exclusively on SMS-based verification.

3. Add a Trusted Contact to Your Financial Accounts

Some financial institutions and brokerage firms allow customers to designate a trusted contact.

A trusted contact is someone the institution may reach if it suspects suspicious activity or has difficulty contacting the account holder.

This feature can provide an additional communication channel if criminals compromise your phone number or attempt to take over your financial accounts.

Check with your bank or brokerage to understand whether this option is available and how it works.

4. Freeze Your Credit Reports

Identity thieves may use stolen personal information to open fraudulent credit accounts or apply for financial products in someone else's name.

A credit freeze can help reduce this risk by restricting access to your credit report for new applications.

In the United States, consumers can request credit freezes through the three major credit bureaus:

• Equifax

• Experian

• TransUnion

You should also review your credit reports regularly and look for unfamiliar loans, credit cards, or other accounts.

5. Monitor Your Bank and Financial Accounts

Regularly reviewing your financial accounts can help you identify suspicious activity before it causes further damage.

Pay attention to unexpected password reset notifications, unfamiliar transactions, changes to account details, and login alerts.

If you notice something unusual, contact your financial institution immediately through its official website or telephone number.

Warning Signs That Someone Has Taken Control of Your Phone Number

SIM swap fraud can happen without any physical access to your smartphone. However, there are several warning signs that may indicate your mobile number has been compromised.

One of the most common signs is a sudden loss of mobile network service.

If your phone unexpectedly displays "No Service" or loses its cellular connection without an obvious explanation, someone may have transferred your number to another SIM card.

Other warning signs include:

• Unexpected loss of service: Your phone suddenly stops receiving calls, text messages, or mobile network signals.

• Suspicious carrier notifications: You receive a message or email about a SIM change or number transfer you never requested.

• Unexpected password reset messages: You receive account recovery notifications that you did not initiate.

• Banking alerts: Your bank notifies you about unfamiliar logins, transactions, or account changes.

• Locked accounts: You suddenly cannot access your email, banking, or other important online accounts.

• Missing verification codes: One-time passwords and security messages stop arriving on your phone.

A loss of service does not automatically mean SIM swap fraud. Network outages, damaged SIM cards, and technical problems can cause similar symptoms.

However, if your service disappears unexpectedly, contact your carrier promptly to determine whether an unauthorized transfer has taken place.

What Should You Do If Someone Steals Your Phone Number?

If you suspect SIM swap fraud, acting quickly is essential. Criminals may use their access to your phone number to reset passwords, enter financial accounts, and steal money.

Follow these steps to reduce the potential damage.

Step 1: Contact Your Mobile Carrier Immediately

Use another phone to contact your wireless provider. Explain that you suspect an unauthorized SIM change or number transfer.

Ask the carrier to investigate the account, block unauthorized changes, and restore control of your phone number.

Step 2: Contact Your Bank and Financial Institutions

Immediately notify your bank, credit card companies, and brokerage firms about the suspected attack.

Ask them to secure your accounts, review recent transactions, and block suspicious activity where necessary.

If you believe your account credentials have been compromised, change your passwords using a trusted device.

Step 3: Secure Your Email and Other Important Accounts

Your email account is particularly important because criminals may use it to reset passwords for other services.

Change compromised passwords, enable stronger authentication, and review account recovery settings.

Where possible, remove unfamiliar devices and active login sessions.

Step 4: Report the Identity Theft

In the United States, victims can use the Federal Trade Commission's IdentityTheft.gov website to report identity theft and receive a personalized recovery plan.

The service provides guidance on reporting the incident, protecting accounts, and addressing potential financial damage.

You may also need to submit supporting documents, such as a police report or identity theft affidavit, depending on the financial institution's requirements.

Step 5: Check Your Credit Reports

Review your credit reports for unfamiliar accounts, loans, or applications.

If you discover suspicious activity, contact the relevant credit bureau and financial institution to dispute the information and take appropriate protective measures.

Disadvantages and Limitations of Mobile Number Locks

Although number locks and carrier PINs provide valuable protection, they can sometimes create inconvenience.

For example, customers who want to switch wireless providers may need to disable their number lock before transferring their phone number.

Some carriers also require a separate Number Transfer PIN, which is a temporary security code used to authorize a transfer to another provider.

If you forget your account PIN or cannot access your account, a legitimate carrier switch or phone replacement may take longer than expected.

There are also special protections under the Safe Connections Act for certain domestic violence situations. These circumstances may involve different procedures for separating wireless accounts and transferring numbers.

Another important limitation is that a carrier PIN depends partly on the provider's verification procedures and customer support practices.

This is why carrier notifications are important. If you receive an alert about a SIM change or port-out request you did not authorize, you have an opportunity to contact the provider and challenge the request.

Combining a strong carrier PIN with an authenticator app or security key provides stronger protection than relying on a mobile number alone.

Final Thoughts: Protect Your Phone Number Before Criminals Target It

SIM swap fraud is a serious cybersecurity threat because it can turn an ordinary mobile phone number into a gateway to someone's financial and personal information.

By taking control of a victim's number, criminals may intercept banking verification codes, reset account passwords, and attempt to access sensitive services.

Fortunately, there are practical ways to reduce these risks. Setting up a strong carrier PIN, enabling a number lock, using an authenticator app, freezing credit reports, and monitoring financial accounts can all help protect your identity.

Don't wait until your phone suddenly displays "No Service" to think about mobile security.

Contact your wireless provider today, activate the available account protections, and make sure your most important financial accounts use strong authentication methods.

A few minutes spent improving your security could help prevent significant financial losses in the future.