As months and then years passed, Brill and Holdren kept order- ing drugs. Controlled buys, they knew, would anchor any eventual prosecution. They were struck by how easy it was. RX Limited websites operated like any online store: Customers placed the drugs they wanted into a virtual shopping cart and then "checked out." They filled out the surveys with whatever came to mind, and paid with real credit cards. (Unlike on the more anonymous layers of the Internet that would later become known as the Dark Web, customers didn’t require any special software or online currency to buy drugs.) Two days later, the box would arrive.

But there was one quirk to the system: The investigators noticed that when Brill’s alter ego Sarah Johnson checked out at an RX Limited site like SpeedyRX.com, her browser suddenly "redirected," or switched locations, to another site called Cartadmin.com. The same thing happened on every other RX Limited-related site. In programming parlance, Cartadmin.com and a second site called SystemsCA.com constituted the "back end" of the RX Limited system, the part that processed transactions. These sites, Brill and Holdren realized, were what linked hundreds of RX Limited af- filiate websites together. If an affiliate used Cartadmin.com or SystemsCA.com as its back end, Brill and Holdren now knew that it belonged to Le Roux.

To understand what this all added up to, the investigators had to travel well past the limits of their DEA training and plunge into the technical thicket of the Internet. Their case against Le Roux would be built in part on an understanding of the Internet’s basic ar- chitecture, namely that every computer connected to the network— and every website hosted on it—is assigned a unique number called an Internet Protocol, or IP, address. When Brill typed "Cartadmin .com" into a browser, her request traveled to a domain name server—the Internet equivalent of a telephone directory—which spent a fraction of a second looking up Cartadmin.com and re- turning an IP address for its location. The Internet’s directories are managed, in turn, by an international body called ICANN, short for the Internet Corporation for Assigned Names and Numbers.