AT&T, a Dallas-based telecommunications giant, has confirmed a significant data breach impacting 73 million current and former customers, with personal information including Social Security numbers and passcodes leaked on the dark web. The breach, affecting 65.4 million former customers and 7.6 million current ones, was confirmed by various news outlets and the company itself. AT&T has initiated an urgent investigation to determine the source of the leak, stating that there has been no direct unauthorized access to its systems. The data, from a 2019 breach, includes Social Security numbers and numerical PINs that are typically four digits long. In response, AT&T has changed the account passcodes of millions of its customers and begun notifying affected individuals. The breach has led to a lawsuit against AT&T for allegedly exposing users to privacy-related injuries and has negatively impacted the company's stock, with a pre-market decrease of -2.3% and later -0.3% reported.