A cyber breach is an unauthorized event that compromises a digital system or data. It may involve an attacker accessing confidential information, disrupting services, or changing or destroying data. A breach can result from exploited software vulnerabilities, stolen credentials, misconfigurations, or other security failures.
Breaches matter because they can expose users and organizations to financial loss, operational disruption, and further attacks. In practice, defenders investigate suspected breaches, limit access, preserve evidence, and notify affected parties when required. Organizations also reduce risk through secure development, timely patching, access controls, and monitoring. Determining responsibility after a breach can be complex: the cause, security practices, contracts, and applicable laws may all affect how liability is assessed.