LYON — In ancient Greek mythology, Hercules had to slay the multiheaded serpent-like Hydra, guardian of the underworld, although each time a head was cut off, two others would grow in its place.

In modern sports, it can seem that the authorities face a similar and equally herculean task in the global fight against illegal sports betting and match-fixing.

Michel Platini, the head of UEFA, the governing body of European soccer, which runs the richest sports club tournament in the world, the Champions League, has called illegal betting the greatest danger to the game, “the one that can kill football.”

Jacques Rogge, president of the International Olympic Committee, goes even further.

“Sport is in danger,” Rogge said. “It’s not about the Olympics, it’s not about the Games, it’s about sport in general. Illegal betting in sport generates a turnover of around $140 billion a year, and it is inevitable that the Games will be sullied.”