Anthem (NYSE:ANTM) has been the victim of a huge data breach.

The Anthem data breach may affect 80 million people, including employees of the insurer. The company has promised to contact members affected by the hack and provide them with free credit monitoring and identify protection. The insurer is currently working with the FBI to learn more about the data breach, reports The Washington Post.

The Anthem data breach was the result of hackers breaking into the company’s IT system. Possibly stolen data includes “names, birthdays, medical IDs, social security numbers, street addresses, email addresses and employment information, including income data.” The company has hired Mandiant to look over its security network, The Washington Post notes.

Unfortunately, the Anthem data breach is worse than the average hack because it includes social security numbers. Unlike when debit or credit card information is stolen, a new social security number can’t be easily issued. Even if it could, creditors would still associate a person with their old number, reports Time.

ANTM shares were down slightly as of Thursday afternoon.

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