The current landscape of the core Internet technologies shows considerable centralisation with the big tech companies controlling the vast majority of traffic and services. This situation has sparked a wide range of decentralisation initiatives with blockchain technology being among the most prominent and successful innovations. At the same time, over the past years there have been considerable attempts to address the security and privacy issues affecting the Domain Name System (DNS). To this

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... d, it is claimed that Blockchain-based DNS may solve many of the limitations of traditional DNS. However, such an alternative comes with its own security concerns and issues, as any introduction and adoption of a new technology typically does -let alone a disruptive one. In this work we present the emerging threat landscape of blockchain-based DNS and we empirically validate the threats with real-world data. Specifically, we explore a part of the blockchain DNS ecosystem in terms of the browser extensions using such technologies, the chain itself (Namecoin and Emercoin), the domains, and users who have been registered in these platforms. Our findings reveal several potential domain extortion attempts and possible phishing schemes. Finally, we suggest countermeasures to address the identified threats, and we identify emerging research themes. INDEX TERMS Blockchain, blockchain forensics, cybercrime, DNS, malware. He has participated in several European-, Spanish-and Catalan-funded research projects. He has authored more than 40 publications in peer-reviewed international conferences and journals. His research interests include pattern