The law was desperately needed, but it’s just a start. Worldwide, criminals have enslaved 25 million human beings for forced labor or sexual exploitation—or some combination of the two. Each year, criminals rake in an estimated $150 billion from this “industry.” Google, Facebook, and other Internet and social media giants can help combat this scourge—but not alone.

Banks and other financial institutions, which may unwittingly handle human traffickers’ money, are well-equipped to help. By devoting more resources to identifying traffickers and cooperating with law enforcement agencies, these institutions can bring perpetrators to justice.

Trafficking is a well-known problem in less-developed countries. But it’s also a rampant issue here in the U.S. More than 8,500 cases were reported nationwide in 2017 alone—a 13% increase from 2016.

Trafficking victims suffer immensely. Many are forced to travel thousands of miles between countries. Some die during their initial abduction and transport. Last year, authorities discovered 39 victims trapped in an abandoned truck in the San Antonio heat, nine of whom died. Those who do arrive at their final destinations live in terrible conditions and are constantly exposed to health hazards like HIV/AIDS.

Currently, it’s far too easy for traffickers to dodge the law. In 2016, despite the millions of victims, there were only 9,071 human trafficking convictions globally. Banks and other financial institutions are strategically positioned to change this sad status quo.

Financial institutions can start by stepping up their efforts to identify traffickers, who depend on banks to conduct their operations. Without bank accounts, traffickers would have to carry physical cash, which is much less convenient and tougher to transport. Plus, having piles of cash could make them prime targets for other criminals.

By using banks, traffickers leave behind a slew of financial footprints. For example, traffickers may use so-called “funnel” accounts to transfer large sums of money quickly. In this scenario, money is deposited in an account and then quickly withdrawn from another location. Other red flags include credit card transactions late at night or very early in the morning, purchases on certain classified ad sites, and use of anonymous payment methods rather than personal checks.

Banks can program their systems to automatically flag such behavior. And if human reviewers ultimately confirm the patterns are suspicious, banks can alert law enforcement. Once specially trained investigators and police officers are armed with the financial clues, they can follow the money trail. And prosecutors can help build their cases with the available financial data.

Many financial institutions are already showing how banks and law enforcement can work together to crack down on trafficking.

Consider the efforts of the Iowa-based MetaBank. It developed technology that monitors prepaid cards, which criminals use to transfer funds between countries. When they detect suspicious activity, they share the information with law enforcement. In 2013, several major banks—including JPMorgan Chase, Citigroup, and Bank of America—launched a human trafficking working group with the Manhattan district attorney’s office to collaborate on the best ways to identify trafficking.

Or take the Blue Campaign, a partnership between the Department of Homeland Security, the Treasury Department’s Financial Crimes Enforcement Network (FinCEN), and private financial institutions. FinCEN provides these private organizations with comprehensive instructions on how to detect suspicious financial activity.

The partnership between Canada’s Project Protect and my organization, the Association of Certified Anti-Money Laundering Specialists, offers another example. Launched in 2016, Project Protect is a public-private partnership between Canadian government agencies and private financial institutions. These banks monitor for activity such as irregular deposits and cash flows that may indicate trafficking.

The program has already yielded impressive results. In 2015, financial institutions only submitted 400 reports of suspicious transactions related to human trafficking. In 2016 and 2017, they submitted more than 2,000 each year. The reports have aided several investigations.

Neither law enforcement, Internet firms, nor financial institutions can stamp out human trafficking alone. But when they work together, they can disrupt traffickers’ operations, rescue victims, and ensure justice is served.

Rick McDonell is the former executive secretary of the Financial Action Task Force and the current executive director of the Association of Certified Anti-Money Laundering Specialists.