Such apps surreptitiously load barrages of invisible ads that artificially inflate viewer numbers and eat up as much as two gigabytes of internet data per day on images and videos that are never actually seen, according to the study done by ad fraud detection firm Forensiq.

Such apps can launch battery and bandwidth-intensive operations hidden in the background of the device that linger even after the app is exited, reported Mashable.

The apps - as many as 15 percent of them - request access to settings like preventing the device from sleeping, modifying and deleting memory and tracking your location, which are often unnecessary for the app's purported function.

"We wanted to show the public how blatant and hurtful all this fraud is -- not just to advertisers who pay for ads that no one sees but also people using these apps on these tiny devices that are bandwidth-limited and power-limited," Forensiq's chief scientist Mike Andrews was quoted as saying.

The researchers arrived at this data by tracking the inner workings of ad exchanges, or digital marketplaces that auction off the screen space in front of you to advertisers in real time as a page or app is loading. They analysed more than 16 billion ad views on 12 million devices.

Is there a solution? "From a scientific standpoint, it's really kind of an impossible problem," Andrews said.

Researchers say users can take simple steps to protect themselves from fraud. One is scanning app review sections for accounts of excessive data or power usage that may indicate fraud is at play. Another is switching off access to cell data for apps that do not absolutely need it.