AT&T said at the time that it had already reset the passcodes of current users and would be communicating with account holders whose sensitive personal information was compromised. There's also been major disruptions at car dealerships in North America after software provider CDK Global faced back-to-back cyberattacks. And Alabama's education superintendent said earlier this month that some data was "breached" during a hacking attempt at the Alabama State Department of Education. Shares of AT&T Inc., based in Dallas, fell more than 2% before the markets opened on Friday.