Cybercrime is on the rise and conventional investigative measures are nearly useless against the methods of anonymization and encryption used by cybercriminals. Legalizing „hacking“ for police investigations could form part of the solution to overcome these obstacles. Police-hacking comprises a variety of existing investigative measures in which investigators gain remote access to a device by using malware. This practice entails, however, important legal shortcomings, especially with regard to encroachments on fundamental rights. Therefore, a legal framework providing for specific rules on proportionality and judicial review is needed to ensure full respect of fundamental rights and national constitutional safeguards, without comprising cross-border cooperation among EU and international law enforcement authorities.To this end, the study will perform the first comparative research on the topic, analyzing three European Member States: France, Germany and Luxembourg. All three are, as powerful economies and financial locations, likely to suffer cyber-attacks. Also, they represent different legal traditions, have taken different approaches to police-hacking and find themselves at different stages of implementing corresponding provisions, reasons which make them particularly interesting systems for comparative study. Additionally, fluent cross-border cooperation in criminal proceedings demands common standards for fundamental rights protection in practice. A comparative and European study will provide an innovative, yet significant contribution, to this end.The aspired outcome is threefold: Firstly, to provide the first study on Germany’s recently enacted provisions and the Luxembourg legal draft, the first comparative study and additionally the first European study on the subject. Secondly, to propose a blueprint for a legal framework in the three studied systems and at the EU level that optimally balances investigative effectiveness and fundamental rights. And lastly, to provide for a valuable for scholars, legal practitioners and criminal enforcement agents, confronted with legal issues related to police-hacking in their every-day fight against cybercrime.