Honest investors in public markets—which one way or another refers to most Americans—expect the government to make sure traders and the very exchanges on which they trade are not breaking the rules to rip them off. Whether they know it or not, investors should also be thanking Dodd-Frank whistleblowers for playing a central role in policing both traders and exchanges.

In this era of trading dominated by high-frequency trading strategies that most investors scarcely comprehend, the government can’t play sheriff alone. Many abuses by market participants and financial exchanges have been difficult for the government to detect.

Complex market manipulation strategies are used by traders who are eager to fleece other market participants and exotic order types and other services selectively used by some exchanges have required whistleblowers to expose them to the light of day. Recent government enforcement efforts in these areas have been instigated and aided-and-abetted by expert outsiders. The independent work of these outsiders has helped the government build highly technical enforcement cases.

These particular outsiders are also Dodd-Frank whistleblowers, persons incentivized for the past 7 years to report fraudulent activity to regulators with the prospect of sharing in the bounty when the offenders end up paying the SEC, CFTC, and often DOJ more than $1 million.

Just last week the Department of Justice and the U.S. Commodity Futures Trading Commission announced a spate of settlements with banking giants Deutsche Bank, UBS, and HSBC, as well as criminal charges against several traders and a software developer for engaging in prohibited “spoofing” in futures markets. The banks will collectively pay $47 million, and the traders will face jail time.

Now codified as a felony under the Dodd-Frank law passed in 2010, “spoofing” is a prohibited form of trading where a trader bids or offers in the market with the intent to cancel the bid or offer before execution. Spoofing is market manipulation through pranking. Though it sounds almost whimsical, this particular form of pranking can cost a trader 10 years in prison and treble the monetary gain resulting from the spoofs. Gain, that is, straight from the pockets of honest traders.

The most famous spoofer so far is Navinder Sarao, the British trader who pled guilty after being extradited on charges of market manipulation by DOJ and the CFTC in 2015. As alleged by the government, Mr. Sarao contributed to the May 6, 2010 “Flash Crash” that rocked financial markets and intensified concerns over market integrity in the electronic age. But despite the efforts of the CFTC and the SEC to examine the causes of the Flash Crash, set forth in a lengthy post-mortem report served on Congress, it took a Dodd-Frank whistleblower to identify Mr. Sarao’s pattern of unlawful trading practices.

That anonymous market expert whistleblower brought his findings to the CFTC, which subsequently was able to confirm his allegations and develop a successful prosecution. Building on the success of the Sarao investigation, both the CFTC and DOJ appear to have developed several additional spoofing cases, including those announced this week which appear to include charges against the technical architect of Mr. Sarao’s trading operation.

Dodd-Frank whistleblowers are also policing our financial exchanges.

In the summer of 2011, the same month the SEC officially opened its doors for whistleblowers under the Dodd-Frank whistleblower program, veteran Wall Street electronic trader Haim Bodek contacted the SEC about exchange abuses. Mr. Bodek brought allegations that financial exchanges had violated securities laws and regulations by discriminating against certain traders and favoring others through the use of exotic order types.

The unscrupulous exchanges had offered special order types for special customers, but on the down low. EDGA Exchange and EDGX Exchange variously allowed preferred high-frequency traders to queue jump honest traders through price-sliding functionality offered selectively by the exchanges eager to cater to high frequency traders and their sought-after liquidity.

Mr. Bodek spent years investigating and examining the minutiae of market structure operations. His allegations eventually made their way to the SEC’s Market Abuse Unit, which spent several years investigating and ultimately settling claims in 2015 against the two financial exchanges subsequently acquired by BATS Global Markets. The penalty in that case was then the largest ever against a national securities exchange and the first to focus on stock exchange order types.

Fortunately for investors, despite the stratagems of manipulators and incentives for exchanges to play favorites, Dodd-Frank whistleblowers have changed the trading landscape in equities and futures, and we should expect they will continue to do so. If we want to catch even more financial fraud, Congress should work to further expand whistleblower programs like Dodd-Frank’s.

Shayne C. Stevenson, a partner at Hagens Berman LLP, is counsel to both SEC whistleblower Haim Bodek and the anonymous CFTC “Flash Crash” whistleblower.