1. and 2. Yahoo
Yahoo takes the cake when it comes to data breaches. Two breaches that their systems have undergone hold the top two places on this list. In September of 2016, Yahoo announced that two years prior 500 million Yahoo accounts had been breached. The evidence, according to Yahoo, pointed to a state-sponsored actor. A few months later, at the end of 2016, another Yahoo hacking incident came to light. A much bigger one. Yahoo announced that in August of 2013, 1 billion accounts had been breached, making it the largest hack on record. From the evidence that investigators found, the two hacking incidents were not linked. However, in both hacking incidents, everything from dates of birth and email addresses to encrypted security questions and answers and hashed passwords were stolen. Fortunately, no financial information was taken.