An anonymous reader writes: Credit card numbers are constantly being stolen, but the people who take them don't usually use them. Instead, they sell them to others who will. Many cards are traded at online forums and markets. Law enforcement investigators know this, and they use these forums to gather intelligence on breaches. But Brian Krebs writes that one of the biggest markets, Rescator, has implemented methods to screen out suspected law enforcement agents. Krebs says of a law enforcement source of his: "The criminals running the fraud shop seized his carding store account and bitcoin balance after the pig alert flashed on my source's screen — effectively stealing hundreds of taxpayer dollars directly from the authorities. .. I found his case fascinating and yet another example of the growing sophistication of large-scale cybercrime operations."