Wi-fi warning: When you connect to public wi-fi, you're making it easier for companies to track your location and place "pop up" ads on your phone.
Many apps leak personal information.
The Wall Street Journal recently tested 101 popular apps.
They found 65 of them transmitted the phone's unique ID number to other companies without your consent.
Forty-seven of them transmitted the phone's location.
And a handfull sent other personal information to online tracking companies.