If there’s one thing Robert Khuzami learned from his experience prosecuting the first World Trade Center bombers in 1995, it’s this: “Whether you’re dealing with terrorism or securities fraud, it’s better to be in the prevention business than the cleanup business.”

As the top cop at the U.S. Securities and Exchange Commission, Khuzami has spent his first six months as the director of the Division of Enforcement tackling a cleanup of major proportions. He’s undertaken what many call the most sweeping changes of the division in 30 years, a top-to-bottom overhaul of how the agency detects and prosecutes wrongdoing in the financial marketplace.