Between May and July 2017, hackers broke into credit reporting agency Equifax's systems to access the data of more than 143 million users. Though Equifax later bumped up the figure to 145 million, security experts put the number of affected users at around 147.9 million. It is one of the most damaging data breaches in history. However, Equifax didn't report the breach until September 2017. Hackers had amassed vital information about millions of people, including names, street addresses, driver's license numbers, birth dates, and even social security numbers. Hackers exploited a vulnerability in the open-source software Apache Struts to access its servers.