1. Ability to make use of any information system (IS) resource. NIST SP 800-32.

Source: Committee on National Security Systems Glossary, CNSSI 4009-2015, National Security Agency,; The State and Local Election Cybersecurity Playbook Defending Digital Democracy Project Harvard Kennedy School Belfer Center for Science and International Affairs,

2. The ability and means to communicate with or otherwise interact with a system, to use system resources to handle information, to gain knowledge of the information the system contains, or to control system components and functions.

Source: The Cyber Glossary, National Security Archive, George Washington University,; National Initiative for Cybersecurity Careers and Studies, Explore Terms: A Glossary of Common Cybersecurity Terminology, National Initiative for Cybersecurity Careers and Studies (NICCS),

3. Entry into an information or operational technology system.

Source: U.S. Cyberspace Solarium Commission, March 2020,