Of all our most closely held data—birthday, mother’s maiden name, bank details—the one we desire to keep most secure is our social security numbers. With it, other personal information, including tax data and other personally identifiable information (PII) is easier to extract. And now, even THAT has come under attack.

National Public Data, a company that performs background checks, confirmed nearly 3 billion records (including names, addresses, contact information, AND SSNs) were stolen. This data breach affects millions of Americans, all of whom were notified by NPD that their data was likely stolen during a December 2023 hack by the cybercriminal group USDoD.

A class action suit has been filed by Schubert, Jonckheer & Kobefor those who have been affected, and another security firm, Pentester, has developed a tool to determine if you are one of the unlucky victims of this crime. You can visit https://npd.pentester.com and enter non-sensitive information to see if you’ve been targeted.

If you are on this list, security experts recommend freezing credit reports since SSNs are used to secure loans or to apply for credit cards. If you’ve suffered financial loss from this breach, you may want to reach out to an attorney or join the class action suit.

If you are not on the list, it’s still good practice to regularly monitor your credit and to use the opportunity to delete cookies on your computer and reset all your passwords.