A U.S. regulator is trying to teach stock brokers to identify when their clients are engaging in a form of market manipulation known as spoofing.

Thomas Gira, executive vice president of market regulation at the Financial Industry Regulatory Authority, said the organization is running a program with five companies that lets them know when Finra sees behavior among customers that looks like spoofing. Finra has rolled the pilot into its equity report card system, which provides a snapshot of compliance with equity trading rules, he said.

“We’re not giving away the secret sauce, but we’re telling firms, this is what we’re looking for,” Gira said at a financial markets conference Wednesday at Baruch College in New York. “We’re hoping that will educate firms. They can see the conduct that emanated from them that we flagged.”

Gira didn’t provide further details of the effort, or name the firms involved. Finra said in January that it would start a pilot program that used its cross-market surveillance ability to help firms spot and prevent manipulative trading activity.

The Finra effort comes as authorities overseeing futures markets -- an area that Finra does not regulate -- have stepped up their enforcement of spoofing, a practice of tricking other investors by entering buy or sell orders with no intention of filling them. While it’s been outlawed in equities since the 1930s, the strategy was made illegal in futures by the 2010 Dodd-Frank Act. Last week, a high-speed commodities trader, Michael Coscia, was found guilty of spoofing in under an hour by a Chicago jury.

Defining spoofing has proved slippery, according to some. Gregg Berman, a principal at Ernst & Young LLP and a former official at the U.S. Securities and Exchange Commission, said there is a “fine line” between legitimate market-making practices and what is considered spoofing.

In an increasingly automated world trading algorithms could inadvertently end up engaging in practices that may be considered spoofing, posing headaches for chief compliance officers, he said at a later panel at the Baruch event.

“If I was a CCO, I would be paranoid,” Berman said.