Securing the United States against cyber attacks has become one of the nation’s highest priorities. To achieve this objective, networks, systems, and the operations teams that support them must vigorously defend against external attacks. Furthermore, for those external attacks that are successful, defenses must be capable of thwarting, detecting, and responding to follow-on attacks on internal networks as attackers spread inside a compromised network.
A central tenet of the U.S. Comprehensive National Cybersecurity Initiative (CNCI) is that "offense must inform defense." In other words, knowledge of actual attacks that have compromised systems provides the essential foundation on which to construct effective defenses. The Senate Homeland Security and Government Affairs Committee moved to make this same tenet central to the Federal Information Security Management Act in drafting FISMA 2008.