Breach occurred on July 29 exposing PII including social security numbers, birthdays, address, credit card numbers and more.
Stock shares dropped nearly 6% during after hours trading.
Equifax Inc., which supplies credit information and other information services, said Thursday that a cybersecurity incident could have potentially affected 143 million consumers in the U.S. The U.S. Census Bureau said the U.S. population was about 324 million people as of January 1, 2017, which means this affects a huge portion of the United States. Equifax said it discovered the breach on July 29. "Criminals exploited a U.S. website application vulnerability to gain access to certain files," the company explained. Leaked data includes names, birth dates, social security numbers, addresses and potentially drivers licenses. 209,000 U.S. credit card numbers were also obtained, in addition to "certain dispute documents with personal identifying information for approximately 182,000 U.S. consumers."