The internet turned credit card fraud into an industry.

If you had your credit card information stolen between 2002 and 2004, there’s a good chance it was resold on ShadowCrew, an online forum that quickly became something like a social media network for cybercriminals. And if you had it stolen between 2005 and 2008, it was likely resold on ShadowCrew’s successors, CardersMarket or DarkMarket. On these forums, criminals didn’t just sell card information. Thousands of criminals posted day and night, sometimes comparing notes on the best methods of creating counterfeit credit cards and fake IDs, sometimes just chatting about their lives. The forums became their social life. Online, they found not just more criminal opportunities, but a sense of belonging.

If a criminal could get into an online database of credit card numbers, they had access to not just one person’s credit line, but thousands, even millions of them. In the late 1990s and early 2000s, as commerce and financial databases went online, law enforcement were alarmed by the scale and complexity of this new kind of crime.

The FBI and Secret Service organized massive international busts to bring down the leadership of the forums, but time and again, the masterminds of the operations slipped away. The result was an ongoing cat-and-mouse game between police and thieves, featuring complex undercover operations, prison breakouts, and some of the largest—and most costly—data breaches in history.

The economy of stolen data is massive and mysterious. For the second episode of our Kernel Panicseries, we explore the most devastating hacks and exploits in the history of the internet. We spoke to Brett Johnson, the administrator of ShadowCrew, Kimberly Peretti, the prosecutor who brought him down, and Keith Mularski, the FBI agent who went undercover on DarkMarket for two years posing as a spammer, while secretly running the forum from FBI servers.

With real footage of the forums and the insight of the actual criminals and law enforcement agents who defined this brand new kind of crime, we pull back the curtain to show you how these entirely digital crime syndicates worked.