Normally, if enterprise IT security professionals know about a potential threat in advance, they can take steps to mitigate or prevent the damage.

However, when the Izz ad-Din al-Qassam Cyber Fighters telegraphed its pending action against major U.S. financial institutions in September, banks were not able to stop the distributed denial of service (DDoS) attacks, resulting in some disruptions to banking websites and the ability for customers to access information and complete transactions.

"The attack in September was probably the largest DDoS attacks in history," said John M. "Mike" McConnell, the former Director of National Intelligence (DNI) and current vice chairman of Booz Allen Hamilton at the Bloomberg Link Enterprise Risk Conference. "The interesting thing is they announced it in advance."