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, https://rmf.org/wp-content/uploads/2017/10/CNSSI-4009.pdf; The State and Local Election Cybersecurity Playbook Defending Digital Democracy Project Harvard Kennedy School Belfer Center for Science and International Affairs, https://www.belfercenter.org/sites/default/files/files/publication/StateLocalPlaybook%201.1.pdf
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, https://nsarchive.gwu.edu/news/cyber-vault/2018-09-19/cyber-glossary; National Initiative for Cybersecurity Careers and Studies, Explore Terms: A Glossary of Common Cybersecurity Terminology, National Initiative for Cybersecurity Careers and Studies (NICCS), https://niccs.us-cert.gov/about-niccs/glossary
3. Entry into an information or operational technology system.
Source: U.S. Cyberspace Solarium Commission, March 2020, https://subscriber.politicopro.com/f/?id=00000170-c638-d8f7-a7f1-f63b33510000