Illustration by Alex Castro / The Verge

Billions of dollars have been stolen from investors over the last few years by people pretending to be Musk and others. Politicians and law enforcement are turning their attention to Apple and other app stores and how they review fraudulent apps.

In letters to Apple CEO Tim Cook and Google CEO Sundar Pichai on Thursday, Sen. Brown asked that the companies explain their processes in reviewing and approving applications for download on their app stores. According to the FBI report, more than 200 investors have been fleeced out of over forty million dollars from fraudulent cryptocurrencies apps.

It is “imperative that app stores have the proper safeguards in place to prevent against fraudulent mobile application activity”

The senator wrote to Cook about the public being able to download cryptocurrencies through the app store. There are reports of fakecryptocurrencies apps that have tricked hundreds of investors into investing in them.

Requests for comment were not immediately responded to.

Several federal law enforcement agencies, including the FBI and Justice Department, began taking action against scam artists earlier this month. The prevalence of scam has continued to grow despite the fall in price of Cryptocurrencies.

Brown wrote to the CEOs asking them to detail their app review and monitoring processes to prevent it from morphing into a scam. He wants to know if Apple and Google gave consumers with fake investment apps.

It is imperative that app stores have the proper safeguards in place to prevent against fraudulent mobile application activity, as well as firms that offer such services that should take the necessary steps to prevent fraudulent activity.

The Senate Banking Committee, chaired by Brown, was set to hold a hearing with experts on how Congress could better protect investors in the securities markets.

The senator has until August 10th to get a response from the two tech giants.