Anthem Inc., the nation's second-largest health insurer, has said that hackers broke into their database and stole personal information of about 80 million of its customers and employees.

The Wall Street Journal reports the incursion, which was discovered last week, is being investigated.

Anthem said "tens of millions" of records were stolen, including such personal information as names, dates of birth, addresses and Social Security numbers. The breach, according to the health insurer, does not seem to include medical information or financial details, like credit card or bank account numbers.

The investigation has not yet discovered how the hackers were able to obtain the identification information needed to access the database, according to Thomas Miller, the insurer's chief information officer.

Since the attack, Anthem has reset employee passwords with high-level access to its data systems, and has blocked all access that uses only one password, Miller said.

Anthem, who detected the breach itself, has hired FireEye Inc.'s Mandiant cybersecurity unit to investigate. The FBI is also investigating.

A spokesman for the FBI told WSJ the agency is "aware of the Anthem intrusion and is investigating the matter." The agency praised Anthem for its "initial response in promptly notifying the FBI after observing suspicious network activity."

The Anthem data breach could rank among the largest of recent attacks.

Contact information for about 76 million households was stolen in the J.P. Morgan cyberattack. The Home Depot data breach involved 56 million customer credit-card accounts and 53 million email addresses. Hackers stole an estimated 40 million payment cards from Target's database.

Indianapolis-based Anthem, formerly known as WellPoint, provides health insurance coverage for approximately 37.5 million people. The company offers Blue Cross Blue Shield health insurance plans in California, New York, Colorado, Connecticut, Georgia and more states.

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