As enterprises increasingly rely on digital storage systems to manage critical data, insider threats have emerged as one of the most persistent and damaging security challenges. Unlike external attacks, insider threats—originating from employees, contractors, or trusted third parties—are often difficult to detect and mitigate due to their inherent access privileges and knowledge of internal systems. This paper presents a comprehensive security framework aimed at mitigating insider threats in enterprise storage environments, with a specific focus on ensuring data integrity and enforcing robust access control. Through a detailed evaluation of real-world incidents, industry best practices, and current research, we examine how advanced identity and access management (IAM), data loss prevention (DLP) technologies, behavioral analytics, and encryption mechanisms can work together to create a resilient defense posture. We also explore the role of Zero Trust Architecture and continuous monitoring in limiting the potential damage caused by malicious or negligent insiders. The proposed framework integrates technical, procedural, and organizational safeguards, offering a scalable and adaptive approach to protecting sensitive data across on-premises and cloud-based storage systems. By addressing both the technical and human dimensions of insider risk, this study contributes actionable insights for cybersecurity professionals, enterprise architects, and policymakers committed to safeguarding data assets in an era of complex and evolving internal threats.