Illegal property flipping usually often involves collusion between a real estate appraiser, a mortgage originator and a closing agent.

And the Clinton administration and the House Judiciary Committee have asked the Federal Trade Commission to look into whether the increases involve price gouging or collusion.

More mundane cheating involves collusion between players, or the use of multiple accounts by a single player.

The project involved "corruption, collusion and nepotism," the weekly newsmagazine Tempo said in a recent editorial that accompanied a long investigative article on the project.

"The most dangerous kind of cheat, the one that everybody's afraid of, involves collusion, where you have a dealer or somebody who works in the warehouse where they store the cards, in cahoots with a player."

It involved collusion between several high-ranking members of the Imperial Japanese Navy, the British company Vickers and the German industrial conglomerate of Siemens AG.

"Our investigations reveal that investment consultant pay-to-play schemes involving collusion with money managers have cost funds amounts ranging from 10 to 15 percent of assets," Mr. Siedle said.

He added, "If the fraud involves collusion among a number of people, the ordinary auditing procedures wouldn't necessarily uncover it."

But under his tenure, the agency has remained focused on anticompetitive conduct in the health care industry and has brought a number of significant cases involving collusion by drug makers.

"Now it usually involves collusion with someone in the store."