Security: A violation or imminent threat of violation of computer security policies, acceptable use policies, or standard security practices. An occurrence that actually or potentially jeopardizes the confidentiality, integrity, or availability of an information system or the information the system processes, stores, or transmits or that constitutes a violation or imminent threat of violation of security policies, security procedures, or acceptable use policies. ITIL: An unplanned interruption to an IT service or reduction in the quality of an IT service.