Put simply, cybersecurity is the ability to protect or defend the use of cyberspace from cyber attacks, with cyberspace being defined as a global domain within the information environment consisting of the interdependent network of information systems infrastructures including the Internet, telecommunications networks, computer systems, and embedded processors and controller. Source: Committee for National Security Systems Instruction 4009 (CNSSI-4009)
The activity or process, ability or capability, or state whereby information and communications systems and the information contained therein are protected from and/or defended against damage, unauthorized use or modification, or exploitation. Extended Definition: Strategy, policy, and standards regarding the security of and operations in cyberspace, and encompass[ing] the full range of threat reduction, vulnerability reduction, deterrence, international engagement,incident response, resiliency, and recovery policies and activities, including computer network operations,information assurance, law enforcement, diplomacy, military, and intelligence missions as they relate to the security and stability of the global information and communications infrastructure. (Source: National Initiative for Cybersecurity Careers and Studies)