1. An attack that prevents or impairs the authorized use of information system resources or services.
Source: Explore Terms: A Glossary of Common Cybersecurity Terminology, National Initiative for Cybersecurity Careers and Studies (NICCS), https://niccs.us-cert.gov/about-niccs/glossary
2. The prevention of authorized access to resources or the delating of time-critical operations.
Source: 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
3. A DoS attack is an automated attempt to “flood” or overwhelm an organization’s server or website with requests, causing it to be unavailable to legitimate users.
Source: Guide to Cybersecurity as Risk Management: The Role of Elected Officials, Governing Institute, CGI, https://www.cgi.com/sites/default/files/2019-03/guide_to_cybersecurity_as_risk_management_the_role_of_elected_officials_0.pdf
4. An attempt to overwhelm a server’s capacity with traffic so that it is unable to perform its usual duties and respond to its intended users.
Source: Independent Panel on Internet Voting, British Columbia, https://elections.bc.ca/docs/recommendations-report.pdf
5. Have the goal of causing a loss of a specific service to users or at least to considerably restrict the accessibility of the service.
Source: Information Assurance Situation in Switzerland and Internationally, Reporting and Analysis Centre for Information Assurance MELANI, https://www.newsd.admin.ch/newsd/message/attachments/11945.pdf
6. A type of cyber action designed to prevent users from accessing a network-connected service by sending legitimate requests from one source to overload a network’s resources.
Source: U.S. Cyberspace Solarium Commission, March 2020, https://subscriber.politicopro.com/f/?id=00000170-c638-d8f7-a7f1-f63b33510000