How to check if your data was exposed in the AT&T breach

Malwarebytes reports that AT&T has notified authorities of a large data breach exposing tens of millions of current and former customers (reported figures range from ~51M to 73M), including sensitive PII such as SSNs, names, dates of birth and encrypted login passcodes (which researchers found easy to decipher). The article ties the leak to an earlier claim by the cybercriminal group 'Shiny Hunters', notes AT&T reset customer passcodes and has not disclosed a source, and warns that the exposed PII—published publicly rather than only on the dark web—poses a high risk for identity theft.