How to tell if your AT&T data has been leaked
Regardless of whether customer data comes from the direct beach of AT&T systems or via a third party, the end result is the same. The information is there and can be used by malicious actors to obtain more data from the victim.
Some data, such as your name, address, and phone number, is in plain text, but more sensitive data, such as your social security number and date of birth, is encrypted. But before you breathe a sigh of relief, the data set also includes files to decrypt these, so it's best to assume everything is available.
Verifying 70 million records is nearly impossible, but security researchers such as Troy Hunt have already examined the data and confirmed the validity of some of it.
If you were an AT&T customer through August 2021, you may want to visit Troy's excellent site, haveibeenpwnd.com. Troy records his affected AT&T accounts there. Just search for the email you used for your AT&T account and you'll know if it's been compromised.
If you've been affected, we recommend changing your password as a best practice, but be aware that no passwords appear to be collected in this data. but, password security is more important than ever and it's better to be safe than sorry.
You should also be aware of the possibility of phishing and other hacks. Once this data is exposed, attackers can use it to conduct fraudulent campaigns. Always be aware of yourself and be wary of unsolicited emails and phone calls, especially those purporting to be from his AT&T.