Wall Street Journal: What They Know

Marketers are tracking smartphone users through "apps" - games and other software on their phones. Some apps collect information including location, unique serial-number-like identifiers for the phone, and personal details such as age and sex. Apps routinely send the information to marketing companies that use it to compile dossiers on phone users. As part of the What They Know investigative series into data privacy, the Journal analyzed the data collected and shared by 101 popular apps on iPhone and Android phones (including the Journal's own iPhone app). This interactive database shows the behavior of these apps, and describes what each app told users about the information it gathered.

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