Virtual Power Plants (VPPs) represent a critical advancement in modern energy management, aggregating distributed energy resources (DERs) to enhance grid reliability and operational efficiency. However, the increasing digitization and interconnectivity of VPPs expose them to significant cybersecurity threats. This article explores the concept of cyber resilience in VPPs, emphasizing the need for robust security frameworks that ensure continued functionality even in the face of cyberattacks. We propose cyber-resilient VPP architecture that incorporates multi-layered anomaly detection, real-time threat mitigation, and adaptive control mechanisms. The study outlines a hierarchical control structure within VPPs, where primary controllers manage local DER stability, secondary controllers optimize cluster-level energy coordination, and tertiary controllers handle system-wide forecasting and market participation. Each layer presents unique vulnerabilities to cyber threats, requiring specialized defensive strategies. Advanced techniques such as software-defined networking (SDN) and blockchain-based secure transactions are explored to fortify VPP communications and prevent unauthorized access. Additionally, human-in-the-loop considerations highlight the importance of operator training, cognitive analysis, and adaptive response strategies in mitigating cyber risks. A key innovation discussed is the implementation of dynamic watermarking techniques for real-time detection of cyber intrusions at the sensor layer, ensuring data integrity and operational stability. A hardware-in-the-loop (HIL) testbed is employed to simulate these cyberattacks, demonstrating the effectiveness of anomaly detection frameworks in safeguarding VPP infrastructure. The findings underscore the necessity of integrating cybersecurity with operational strategies to build resilient VPPs capable of sustaining energy delivery under adversarial conditions. By adopting a multi-scale, multi-layer approach to cybersecurity, VPPs can enhance their robustness against emerging cyber threats while maintaining grid reliability and efficiency.