Five Nigerian criminal gangs are behind most scams targeting sellers on Craigslist, study says. They’re using professional check-writing equipment plus U.S.-based accomplices to not raise suspicions among their victims. The most profitable buying-related fraud didn’t involve spoofing fake payments from PayPal. The fake check scam is much more profitable than PayPal scams that try to dupe the person into thinking they will be paid from an escrow account when an item is shipped. Researchers seeded Craigslist with ads for laptops to attract scammers who target sellers.”]