How your phone may be spying on you

These screenshots and videos of your activity on the screen could include usernames, passwords, credit card numbers, and other important personal information, the researchers said.

"We found that every app has the ability to record your screen and anything you type," said David Choffnes, a Professor at Boston's Northeastern University.

The findings will be presented at the Privacy Enhancing Technology Symposium Conference in Barcelona.

For the study, the team analysed more than 17,000 of the most popular apps on the Android operating system, using an automated test programme written by the students.

In all, 9,000 of the 17,000 apps showed the potential to take screenshots.

"There were no audio leaks at all. Not a single app activated the microphone," said Christo Wilson, Professor at the varsity.

"Then we started seeing things we didn't expect. Apps were automatically taking screenshots of themselves and sending them to third parties."

Although these privacy breaches appeared to be benign, they emphasised how easily a phone's privacy window could be exploited for profit.

"This opening will almost certainly be used for malicious purposes. It's simple to install and collect this information. And what's most disturbing is that this occurs with no notification to or permission by users," Wilson noted.

Although the study was conducted on Android phones, there is no reason to believe that other phone operating systems would be less vulnerable, the researchers said.

Another study, published in Headache: The Journal of Head and Face Pain, found that apps developed to help people track their migraine pain often share information with third parties, posing privacy risks partly because there are few legal protections against the sale or disclosure of data from medical apps to third parties.

"In 2018, it is estimated that nearly half of 3.4 billion smartphone users will use health related apps, and currently, there are a wide range of apps on the market for various neurologic and pain conditions," said lead author Mia Minen, from the New York University Langone Medical Center in the US.

"We think our study may have widespread implications for people suffering from various chronic conditions," Minen added.