As Black Friday and Cyber Monday deals continue throughout the holiday season, millions of consumers will log on to snag the best offers of the year. But they aren’t the only ones on the hunt for seasonal discounts. Cybercriminals, too, flock to dark markets, browsing for their version of “steals” on an assortment of unconventional goods and services. In a digital underground that mirrors traditional e-commerce in many ways, these markets cater to buyers with specific — and often illegal needs.