Facebook CEO Mark Zuckerberg speaks at Facebook Inc's annual F8 developers conference in San Jose, California, U.S. May 1, 2018. Stephen Lam | Reuters

Facebook has been paying people to install an app that allows the tech giant to collect data on how they use their smartphones. Since 2016, the social networking giant has been paying teenagers and adults up to $20 a month plus referral fees to install the so-called "Facebook Research" app on their Apple or Android phones, according to tech news site TechCrunch. To mask Facebook's direct involvement, the program is said to be administered through beta testing services Applause, BetaBound and uTest and is referred to as "Project Atlas." A security expert told the publication that the app allows Facebook to collect data including private social media messages, photos and videos sent via instant messaging apps, emails, web searches and web browsing activities. It can also track ongoing location information from other location tracking apps installed in the user's phone, according to the report. A Facebook spokesperson acknowledged the company is running the program to gather data on usage habits and has paid users for their participation.

"Like many companies, we invite people to participate in research that helps us identify things we can be doing better," the spokesperson told CNBC in an emailed statement. "Since this research is aimed at helping Facebook understand how people use their mobile devices, we've provided extensive information about the type of data we collect and how they can participate." "We don't share this information with others and people can stop participating at any time," the spokesperson added. The move from Facebook could potentially be a violation of Apple policy since many of the users on board the program are installing the app on iPhones. Facebook is now pulling the app from all Apple devices following the TechCrunch report. The app will remain available for Android users. In a follow-up statement, the firm said that "key facts" about the research program had been ignored. "Despite early reports, there was nothing 'secret' about this; it was literally called the Facebook Research App," a Facebook spokesperson told CNBC in an emailed statement. "It wasn't 'spying' as all of the people who signed up to participate went through a clear on-boarding process asking for their permission and were paid to participate." The company admitted that teens had participated in the program but clarified that "less than 5 percent" of the people involved were in their teens. "All of them signed parental consent forms," the spokesperson said.