State and non-state actors carry out cyberattacks every day. Cyberspace is currently defined by the DOD as a global domain within the information environment consisting of the interdependent networks of information technology infrastructures and resident data, including the Internet, telecommunications networks, computer systems, and embedded processors and controllers. These systems, as they control the operations of a particular platform, are referred to by the Defense Department as "operations technology." This strategy mitigated the effects of the attack. Had Estonia invoked NATO's Article V collective security provision, doing so would have raised several thorny questions about what kind of attack triggers those alliance obligations. The DOD and U.S. Cyber Command

The Department of Defense is responsible for securing its own networks, the Department of Defense information networks (DODIN), or .mil domain, formerly known as the Global Information Grid (GIG). After recognizing that cyberspace is a global operating domain as well as a strategic national asset, DOD reorganized its cyber resources and established the U.S. Cyber Command in 2010. This sub-unified command under the U.S. Strategic Command is co-located at Fort Meade, Maryland with the National Security Agency (NSA). U.S. Cyber Command operates under U.S.C. Title 10, Armed Forces—the authorities through which the military organizes, trains, and equips its forces in defense of the nation. Subject to such delegation and in coordination with mission partners, specific missions include: directing DODIN operations, securing and defending the DODIN; maintaining freedom of maneuver in cyberspace; executing full-spectrum military cyberspace operations; providing shared situational awareness of cyberspace operations, including indications and warning; integrating and synchronizing of cyberspace operations with combatant commands and other appropriate U.S. Government agencies tasked with defending the our nation's interests in cyberspace; provide support to civil authorities and international partners. Presidential Policy Directive 20, discussed in greater detail below, distinguishes between network defense on the one hand and offensive and defensive cyberspace operations on the other. The following section provides a brief overview of evolving norms in cyberspace and the authorities that govern network defense and cyberspace operations. The U.S. Cyber Command, the military entity responsible for offensive operations in cyberspace and subject to Title 10 authorities, is co-located with and led by the Director of the National Security Agency, a Title 50 intelligence organization. Computer Network Attack, the military parlance for offensive operations, is closely related to and at times indistinguishable from Computer Network Exploitation, which is used to denote data extrapolation or manipulation. 1455 , July 25, 1991, traditional military activities
include activities by military personnel under the direction and control of a United States military commander (whether or not the U.S. sponsorship of such activities is apparent or later to be acknowledged) preceding and related to hostilities which are either anticipated (meaning approval has been given by the National Command Authorities for the activities and or operational planning for hostilities) to involve U.S. military forces, or where such hostilities involving United States military forces are ongoing, and, where the fact of the U.S. role in the overall operation is apparent or to be acknowledged publicly. The directive does not create new powers for federal agencies or the military; however, by distinguishing between network defense and cyber operations, it provides a policy framework for the Pentagon's rules of engagement for cyberspace. In addition to codifying the DECS program, the order provides specific responsibilities to DHS and the sector-specific agencies, as well as the Departments of Commerce, Defense, and Justice, the intelligence community, the General Services Administration, and the Office of Management and Budget, addressed below. International Authorities

The DOD's role in defense of cyberspace follows the body of laws, strategies, and directives outlined above. As discussed, the international community must contend with a certain amount of ambiguity regarding what constitutes an "armed attack" attack in cyberspace and what the thresholds are for cyberattack as an act of war, an incident of national significance, or both. Reports have described the USCYBERCOM cyber force's "National Mission Teams" as protecting the networks that undergird critical infrastructure.
Cyberspace is defined by the Department of Defense as a global domain consisting of the interdependent networks of information technology infrastructures and resident data, including the Internet, telecommunications networks, computer systems, and embedded processors and controllers. Attacks in cyberspace have seemingly been on the rise in recent years with a variety of participating actors and methods. As the United States has grown more reliant on information technology and networked critical infrastructure components, many questions arise about whether the nation is properly organized to defend its digital strategic assets. Cyberspace integrates the operation of critical infrastructures, as well as commerce, government, and national security. Because cyberspace transcends geographic boundaries, much of it is outside the reach of U.S. control and influence.
The Department of Homeland Security is the lead federal agency responsible for securing the nation's non-security related digital assets. The Department of Defense also plays a role in defense of cyberspace. The National Military Strategy for Cyberspace Operations instructs DOD to support the DHS, as the lead federal agency, in national incident response and support to other departments and agencies in critical infrastructure and key resources protection. DOD is responsible for defensive operations on its own information networks as well as the sector-specific agency for the defense of the Defense Industrial Base. Multiple strategy documents and directives guide the conduct of military operations in cyberspace, sometimes referred to as cyberwarfare, as well as the delineation of roles and responsibilities for national cybersecurity. Nonetheless, the overarching defense strategy for securing cyberspace is vague and evolving.
This report presents an overview of the threat landscape in cyberspace, including the types of offensive weapons available, the targets they are designed to attack, and the types of actors carrying out the attacks. It presents a picture of what kinds of offensive and defensive tools exist and a brief overview of recent attacks. The report then describes the current status of U.S. capabilities, and the national and international authorities under which the U.S. Department of Defense carries out cyber operations. Of particular interest for policy makers are questions raised by the tension between legal authorities codified at 10 U.S.C., which authorizes U.S. Cyber Command to initiate computer network attacks, and those stated at 50 U.S.C., which enables the National Security Agency to manipulate and extrapolate intelligence data—a tension that Presidential Policy Directive 20 on U.S. Cyber Operations Policy manages by clarifying the Pentagon's rules of engagement for cyberspace. With the task of defending the nation from cyberattack, the lines of command, jurisdiction, and authorities may be blurred as they apply to offensive and defensive cyberspace operations. A closely related issue is whether U.S. Cyber Command should remain a sub-unified command under U.S. Strategic Command that shares assets and its commander with the NSA. Additionally, the unique nature of cyberspace raises new jurisdictional issues as U.S. Cyber Command organizes, trains, and equips its forces to protect the networks that undergird critical infrastructure. International law governing cyberspace operations is evolving, and may have gaps for determining the rules of cyberwarfare, what constitutes an "armed attack" or "use of force" in cyberspace, and what treaty obligations may be invoked.