A data breach is an incident where unauthorized individuals gain access to sensitive information, potentially leading to identity theft, financial loss, and compromised organizational integrity. Prevention strategies include implementing strong encryption, regular security audits, and employee training on cybersecurity best practices. Additionally, organizations can adopt measures like multi-factor authentication and data access controls to minimize risks. Rapid response plans should be in place to address breaches swiftly, mitigating damage and restoring trust among stakeholders.