A major cybersecurity breach at credit reporting agency Equifax (NYSE:EFX) has exposed the sensitive personal data of up to 143 million Americans. The compromised information included Social Security numbers, birth dates driver’s licenses, and home addresses. The credit card numbers for 209,000 consumers and credit dispute documents for 182,000 others were also exposed in the breach. Personal data about British and Canadian consumers was also compromised.

Richard F. Smith, the company’s chief executive, said in a statement, “This is clearly a disappointing event for our company, and one that strikes at the heart of who we are and what we do. I apologize to consumers and our business customers for the concern and frustration this causes.”

Equifax said the breach, which began in May, was discovered in late July. The company said the hackers exploited a “website application vulnerability” to gain access to information that are the ingredients for identity theft, fraud, and other crimes. The company did not respond to questions about why it waited six weeks to disclose the hack.

This could be one of the largest data breaches in the United States. The company is one of the largest U.S.-based credit reporting agencies. The company operates in 24 countries, holds data on more than 820 million consumers worldwide, and has data for 91 million businesses. The company also manages a database with employee information from more than 7,100 employers.

Equifax serves as one of the three major clearinghouses for Americans’ credit histories. It gets its data from credit card companies, banks, retailers, and lenders. The company is also involved in the collection and sale of consumer data. In 2012, the Federal Trade Commission accused Equifax of inappropriately selling thousands of lists of consumers’ data to third parties.

Equifax is alerting those affected by mail and has set up a website to help consumers at equifaxsecurity2017.com. The company is offering one year of free identity theft protection and credit monitoring to anyone who may have been affected. The company also recommends that consumers review account statements and credit reports to check for incidents of fraud. Consumers can request a free copy of their credit report online at www.annualcreditreport.com from each of the three credit reporting agencies once a year.

Equifax is working with law enforcement and an independent cybersecurity research firm on an investigation of the breach. It said its investigation will be completed in the coming weeks. The Federal Bureau of Investigation is also tracking the situation. Equifax shares fell 12 percent in after-hours trading after the company disclosed the hack.

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