How to stop iPhone SIM spoofing attacks with Verizon, T-Mobile, AT&T, and more.

Major US carriers are working to improve account security to prevent a notorious hack used by scammers called SIM spoofing (or transfer scams). However, Verizon offers something more than the competition with the “Number Lock” peculiarity. Read on to stop SIM spoofing attacks on iPhone.

Recall that SIM spoofing attacks cards is when someone fraudulently transfers your phone number to another SIM card/phone, which can allow them to access many of your other accounts.

This year we have seen major carriers US Communications is rolling out additional security features to help deal with the nasty hack – all major carriers have a separate security PIN for porting numbers to another SIM.

T-Mobile launched this last spring and AT&T says “in most cases we will require you to provide this password before any significant changes can be made, including a transfer initiated through another operator.” But Verizon goes even further with “Number Lock”

How to stop iPhone SIM spoofing attacks (US carriers)

It is important to use all the security levels offered by your carrier. But PINs can be compromised through social engineering and other tactics. That's why we'd love to see T-Mobile and AT&T implement a lockout switch like Verizon has. It's probably not impenetrable, but it's certainly an improvement that all carriers should offer.


Without number blocking, Verizon requires you to generate a PIN to pass the number forward to the port. But here's how to turn on the valuable extra SIM lock switch:

  1. Open Verizon app
  2. Tap Discover tab on the left and see if there is an option to enable number blocking at or near the top
    • If not, tap Account tab bottom > Edit profile & settings at the top
  3. Swipe down from the bottom of the Security section and select Number Block
  4. Tap < strong>switches next to your phone numbers to prevent SIM card portability
  • You can also find Verizon's security settings/number blocking feature online at this link< /li>

This is what it looks like in the Verizon app:

T -Mobile

For T-Mobile, some accounts use a shared account PIN and some require a temporary logout PIN. You can verify that your shared T-Mobile PIN is strong or update it by doing the following:

  • Open the T-Mobile app
  • Click More
  • Select Profile Settings
  • Select T-Mobile ID
  • Select PIN/Password
  • Enter and confirm your PIN/Password or new PIN/Password
  • Click Save – You’will receive a text confirming your PIN/Password update request.

For more information about PINs, visit the T-Mobile support page. And don't forget to leave a review asking for more security for your account and SIM!


Most AT&T accounts require a specific number. Pass the PIN, but it's important to make sure you have a shared account PIN set as a second level of security.

  • Go to your AT&T profile
  • Search my linked accounts.
  • Select Edit next to the passcode you want to change.
  • Follow the instructions.

Learn more about AT&T’ and PIN codes for number transmission. And don't forget to leave a review asking for more security when it comes to your account and SIM card!

Other carriers

  • Check your carrier security app SIM cards or call support for available options.

Additional 9to5Mac Guides:

  • Top mobile carriers: Verizon and T-Mobile vs. AT&T
  • Best Affordable iPhone Data Plans for 2022
  • 5G Home Internet Comparison: T-Mobile vs. Verizon Price, Speed, and Benefits

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