Taxonomy, flexibility, and open issues on pue attack defenses in cognitive radio networks

Primary user emulation attacks (PUEAs) are one of the most damaging threats in cognitive radio networks. Malicious or selfish secondary users pretend legitimate primary users to profit from the opportunistic use of the licensed frequency spectrum. Since cognitive radio importance has enhanced as an approach to spectral efficiency and to diminish the negative effects of wireless network scalability, approaches for PUEAs defense have arisen, evolving their architectural strategy, node's operation and analysis design. This article overviews recent achievement in PUEA defenses and presents a classification. Persistently unsolved challenges in the field are highlighted, and a framework for tackling one of the main challenges - the lack of flexibility to address this highly compromising attack - is outlined, promoting progress in the art of PUEA defense. As proof of concept, results present improvements in attack analysis employing flexible and multidimensional techniques on a case study. Finally, open issues and future directions are emphasized.