AT&T is launching a new Account Lock feature that’s designed to protect wireless users against SIM swapping attacks. The feature, which you can enable from the myAT&T app, prevents unauthorized changes to your account, like phone number transfers, SIM card changes, and updates to billing information.

SIM swapping attacks have become increasingly common in recent years. They occur when a bad actor gets ahold of a victim’s phone number, sometimes with social engineering techniques such as impersonating a victim and asking their carrier for a SIM change, and then intercepting messages and phone calls meant for the victim. This can let an attacker receive two-factor authentication codes that they can use to break into sensitive accounts.

Other carriers, including T-Mobile, Verizon, and Google Fi, already have similar features to prevent against this type of fraud. AT&T began gradually rolling out Account Lock earlier this year.

As noted by AT&T, its new Account Lock feature also blocks device upgrades, along with changes to authorized users and phone numbers. 

You can turn Account Lock on or off at any time by opening the myAT&T app, selecting Services > Mobile Security > Wireless Account Lock, and selecting which accounts you want to lock or unlock.  AT&T will then send the primary account holder an email notifying them of the change, while every active number on the account will receive a text. Only users with primary and secondary access to an AT&T account can use Account Lock.