http://online.wsj.com/article/SB10001424052748703983704576277464260794444.html

APRIL 22, 2011

Avoiding Mobile Trackers

By JENNIFER VALENTINO-DEVRIES

There are ways for users to block the transmission of location information by Android devices and iPhones--although doing so limits important smartphone functions such as maps.

When setting up an Android phone, users are told that the phone may collect their information, but they can uncheck a box and turn location services off at that time. After that point, people can turn location off altogether by going to "menu," "settings," "location" and "location setting."

Android applications must request permission to collect location data before users install them, and users can decide not to download the apps if they don't want them to have that information. But even if a user avoids a particular app, the phone could still send data back to Android maker Google Inc. if overall location services are turned on.

Research has found that transmissions of location data from Android phones sometimes include a unique ID number associated with the phone. Users can change these numbers by performing a "factory reset" of the phone, which deletes the phone's data and settings.

It's also possible to turn off location services on Apple Inc.'s iPhones, by going to "settings" and "general." People who have iOS 4, Apple's latest operating system for mobile devices, also can block an individual app's access to their location by clicking on "location settings" and scrolling down the list of apps. Programs that have transmitted location data in the past 24 hours will be marked with a little arrow on that list.

However, as long as location services are turned on, the iPhone can collect global-positioning system and Wi-Fi information when it is searching for a cellular network, even if the user blocks specific apps.

Researchers revealed this week that iPhones record location information and pass it, unencrypted, to computers that are synchronized with the device. It is possible, though, to encrypt these back-ups. To do that, users can go to the iTunes summary screen when the phone is linked and select "encrypt iPhone backup" under "options." Apple says encrypted backups are indicated by a padlock icon, and a password is required to restore the information to the iPhone. If the password is forgotten, the data will be unrecoverable.