Online drug markets are part of the “dark web”: sites only accessible through browsers such as Tor, which route communications via several computers and layers of encryption, making them almost impossible for law enforcement to track. Buyers and sellers make contact using e-mail providers such as Sigaint, a secure dark-web service, and encryption software such as Pretty Good Privacy (PGP). They settle up in bitcoin, a digital currency that can be exchanged for the old-fashioned sort and that offers near-anonymity during a deal.
Almost all sales are via “cryptomarkets”: dark websites that act as shop-fronts. These provide an escrow service, holding payments until customers agree to the bitcoin being released. Feedback systems like those on legitimate sites such as Amazon and eBay allow buyers to rate their purchases and to leave comments, helping other customers to choose a trustworthy supplier. The administrators take a 5-10% cut of each sale and set broad policy (for example, whether to allow the sale of guns). They pay moderators in bitcoin to run customer forums and handle complaints.