An estimated 143 million people were affected by the breach, which took place earlier this year. Equifax states that it has enlisted an outside cybersecurity firm to investigate the incident and that the issue is currently contained.
Here's what you need to know:
According to Equifax, between mid-May and July, "criminals exploited a U.S. website application vulnerability to gain access to certain files." As a result of the breach, personal information including "names, Social Security numbers, birth dates, addresses and, in some instances, driver’s license numbers" could have been retrieved by the hackers, the company said.
"In addition, credit card numbers for approximately 209,000 U.S. consumers, and certain dispute documents with personal identifying information for approximately 182,000 U.S. consumers were accessed," read a statement from Equifax.
How to know if you're affected
Equifax is encouraging the public to visit the website www.equifaxsecurity2017.com to learn more about the incident and discover whether they are impacted. The site requires individuals to enter some personal information, including their last name and the final six digits of their social security number.
For consumers unwilling to enter the information, Equifax will be mailing notices to people whose "credit card numbers or dispute documents with personal identifying information were impacted."
The agency cautions that they will not be contacting individuals by phone and that members of the public should not provide information to anyone who contacts them about the breach.
What should you do?
Equifax recommends that individuals closely monitor their financial accounts and credit scores for unauthorized activity. The agency is further offering a free year of "identity theft protection and credit file monitoring" through its TrustedID Premier service, and individuals can enroll for the monitoring on the website that confirms whether they are affected.
The Federal Trade Commission also offers advice on its dedicated website for identity theft incidents, www.identitytheft.gov.
Among the steps listed given the parameters of the Equifax breach, the FTC suggests placing a credit freeze or fraud alert, to prevent or make it more difficult for a third party to open accounts using personal information; filing your taxes early to keep others from claiming your refund or using your Social Security number to gain employment; and canceling credit and debit cards and requesting new ones.
TransUnion, which, along with Equifax and Experian, is one of the three major credit reporting agencies, said in a statement that it is evaluating the intrusion to determine any action it may take and that it offers free monitoring services for consumers seeking extra support.
ABC News has reached out to Experian but did not immediately receive a response.