Few devices know more personal details about people than the smartphones in their pockets: phone numbers, current location, often the owner's real name—even a unique ID number that can never be changed or turned off.
These phones don't keep secrets. They are sharing this personal data widely and regularly.
Many smartphone apps collect and broadcast data about your habits.
Many of the app providers don't have privacy policies and there isn't much you can do about it.
It's nearly impossible to prevent cellphone apps, as well as games and other software, from transmitting information about you and your phone.
Turning off the phone's location services can restrict tracking by location. But it can limit some phone features like maps.
Apps sharing the most information included TextPlus 4, a popular iPhone app for text messaging.
It sent the phone's unique ID number to eight ad companies and the phone's zip code, along with the user's age and gender, to two of them.