The rapid development of public surveillance technologies has transformed urban management, public safety, and environmental monitoring. Modern surveillance systems offer high capability for real-time analysis and predictive monitoring powered by artificial intelligence, facial recognition, and IoT integrations. However, this development increases the bar regarding data security, privacy concerns, and ethical implications. This paper presents a holistic review of the current paradigm of public surveillance, discussing major technologies, global regulatory frameworks, and privacy-enhancing techniques addressing these concerns. We present a comparative study of various global case studies to highlight the diverse applications of surveillance systems and the associated ethical, legal, and privacy challenges. We also discuss current research directions on adversarial resilience, multimodal surveillance, and privacy-preserving frameworks. In the light of these, the paper identifies future directions: strong security, ethics in AI, and regulatory alignment to make sure that the surveillance system is aligned with the values of society and respect individual rights. Achieving this balance between technological innovation and ethical responsibility will be of paramount importance as public surveillance continues to expand and in the process of fostering public trust and building a resilient, privacy-conscious digital future. This review contributes uniquely by integrating technological advancements with ethical analyses, offering a comprehensive framework for responsible surveillance practices in the digital age.