The first time NBA forward Jontay Porter tried to cheat DraftKings, by sharing information about his health with a handful of unscrupulous gamblers before a game, a monitoring company called US Integrity knew something was amiss before he set foot on the court. The oddsmakers at DraftKings Inc., the popular online betting service, had spotted wagers that raised instant red flags, and they alerted US Integrity so it could sound an industrywide alarm. Porter’s foolproof scam, it turned out, was actually quite foolish. This was Jan. 26, and after a brief absence because of an eye injury, he was set to return to action that night against the Los Angeles Clippers. Porter was a role player for the Toronto Raptors, averaging just under 14 minutes per game, so he wasn’t in a position to swing the outcome. What he could control, though, was his own box score.

League rules forbid players from betting on NBA games. According to federal court documents filed a few months later, the plan was for his four non-NBA alleged co-conspirators to place proposition bets—wagers on isolated outcomes within a game—on a handful of Porter’s individual statistical categories. Prop bets, offering a wide variety of options, have become a favorite for gamblers. But they’re a particular headache for industry monitors such as US Integrity, because they’re easier to fix than wins and losses. If you can imagine it, some oddsmaker, somewhere, will let you bet on it, from who scores the first touchdown in a football game to whether the game will end with a “scoragami,” a final score never before recorded in NFL play. Pro leagues and oddsmakers are big fans of prop bets, because, says Matthew Holt, US Integrity’s co-founder and chief executive officer, they’re “the greatest engagement and customer acquisition tool we’ve ever seen in sports.” Fans are 20 times more likely to watch a sporting event if they’ve got a bet riding on it, he says, and prop bets keep them watching to the end, even in a blowout. For leagues and television networks desperately trying to hang on to viewers, prop bets are like superglue.