Mary Jo White, the first former prosecutor to serve as chairman of the U.S. Securities and Exchange Commission, has pledged to run a "bold and unrelenting" enforcement program at the agency charged with regulating Wall Street.

With financial crisis cases mostly done and some of the biggest insider-trading cases in history closed, White will have to chart a course into new areas to keep that pledge.

White, who was sworn in last week, has already provided a few signals about what that might be. During her Senate confirmation hearing, she said she intends to focus on high-frequency and automated trading. She has also raised questions about a drop in the number of accounting fraud cases the agency has brought in recent years.