Following the advent of the Internet, the interaction between sellers and consumers is increasingly shifting from a face-to-face towards an online environment. This chapter examines what online consumer fraud is, revisiting the definition and common fraud schemes. It reviews some of the current approaches non-governmental and commercial institutions take to detect and prevent online consumer fraud. The chapter discusses darknet markets – internet platforms that, amongst other things, sell both legal and illicit goods while providing anonymity – and how they facilitating online consumer fraud. It closes with a discussion of how methods from data science can be applied to support the detection and prevention of online consumer fraud. The dark web represents a small portion of the deep web, on which users and hosts are anonymized.