GDPR Article 33 is the breach-notification rule for controllers. It requires a personal data breach to be reported to the relevant supervisory authority without undue delay and, where feasible, within 72 hours after the controller becomes aware of it. If the notification is late, the controller should explain the reason for the delay.
In cyber security, Article 33 matters because speed, evidence, and decision-making become legal requirements, not just operational goals. Attackers may move quickly through stolen credentials, malware, or misconfigured cloud systems, so defenders need strong monitoring, alert triage, and clear incident response ownership. Logs, timestamps, containment actions, and risk assessments help prove when the breach was discovered, what data was affected, and why a notification was or was not made. Good detection and documentation can reduce both regulatory risk and damage from the incident.