What constitutes a security breach?

A security breach is defined as an incident where unauthorized individuals gain access to confidential, sensitive, or protected data, applications, or networks. This can involve various forms of unauthorized access, such as hacking into systems, exploiting software vulnerabilities, or insider threats. The key aspect of a security breach is the nature of unauthorized access, which can lead to data theft, alteration, or destruction, impacting the confidentiality, integrity, and availability of information.

The other options do not fit the definition of a security breach. A successful defense against cyber attacks indicates effective security measures that prevent unauthorized access rather than a breach itself. Multi-factor authentication failures may lead to potential security issues, but a failure itself does not constitute a breach unless it is exploited by an unauthorized party. Scheduled maintenance of network systems is a planned and authorized activity that involves ensuring the systems are running optimally, which does not involve unauthorized access or actions.