This data "abuse" includes sending the identification number of the device, the personal whereabouts of the user, or even the contact details of friends, colleagues and customers, to a server somewhere on the Internet, researchers at Saarland University said.
"My smartphone knows everything about me, starting with my name, my phone number, my e-mail address, my interests, up to my current location," computer science Professor Michael Backes said. "It even knows my friends quite well, as it saves their contact details, too."
Some mobile applications, while displaying simple functionality up front, are busy in the background sending this information to third parties without the user's knowledge, he said.
The researcher's "SRT AppGuard" app determines, for every application installed on a smartphone, what it accesses and displays this information to the user.
The user can revoke or grant those access privileges at any time, the researchers said.
Notable deaths of 2014 [PHOTOS]