Once the attack was discovered, Anthem tried to close the security vulnerability, contacted the FBI and began cooperating with their investigation. Anthem has also retained cybersecurity firm Mandiant to evaluate its systems and identify solutions based on the evolving landscape.
Anthem has started to individually notify current and former members whose information has been accessed.
"Obviously it's quite concerning that we would have yet another intrusion of this size," Michael Daniel, President Barack Obama's cybersecurity adviser said at a seminar organized by Bloomberg Government.
"It's particularly disturbing especially when it hits that many people," Daniel said, advising affected consumers to change their passwords and monitor their credit scores.