Review

The article provides a comprehensive analysis of the legal regulation of covert investigative (search) actions in the context of ensuring human rights amid contemporary security challenges. It examines the conceptual foundations of covert investigations, their historical evolution–from early forms of hidden surveillance to high-tech digital instruments–and the peculiarities of their application in leading democratic states. Particular attention is devoted to the comparative analysis of models in the United States, the United Kingdom, Germany, Switzerland, and Poland, which demonstrate diverse approaches to judicial control, undercover operations, digital surveillance, and institutional oversight. The article also highlights the standards of the European Court of Human Rights regarding interference with private life, including the requirements of legality, necessity, proportionality, effective oversight, and post-factum safeguards. The Ukrainian context is analyzed through the prism of key systemic problems: the formal nature of judicial control, insufficiency of prosecutorial supervision, contradictions between operational-search activity and covert investigative actions, lack of regulation of artificial intelligence, big data, biometric technologies and spyware, as well as the absence of independent external monitoring. It is demonstrated that these factors not only reduce the level of privacy protection but also generate risks of evidence inadmissibility and violations of fair trial standards. The study proposes a structural model for reforming Ukrainian legislation, which includes improving the quality of judicial control, establishing an independent oversight body, introducing procedural regulation of digital technologies, implementing post-factum guarantees, and harmonizing the interaction between operational-search activity and criminal procedure. It is emphasized that the adaptation of foreign standards should follow a model of «flexible implementation,» taking into account the conditions of martial law and the level of security threats. The scientific novelty of the study lies in combining comparative-legal, doctrinal, and technological analysis, which has made it possible to formulate a holistic concept for modernizing the institution of covert investigative actions in accordance with European standards and ECtHR practice. The practical significance is reflected in the identification of specific legislative and institutional solutions capable of ensuring a more effective balance between the interests of national security and human rights protection under conditions of digitalization and hybrid threats.