Parents of online teens are concerned about what exactly their kids do online, but they're also wary of how their children are being tracked by advertisers, according to a new report.

The findings come at a time when the Federal Trade Commission is reviewing the Children's Online Privacy Protection Act (COPPA), a law passed nearly 15 years ago to require websites to get parental permission before collecting data about children ages 12 and younger. The FTC is considering updating COPPA to reflect an era of lives lived on cellphones, apps and social media sites, where data collection has become the norm and not the exception.

"Parents are anxious about a wide range of online risks for their children, but it is particularly striking that their current level of worry about data collection by advertisers meets or exceeds other concerns about their child's online activity," said Mary Madden, research associate for the Pew Internet Project, and co-author of the report, "Parents, Teens and Online Privacy," said in a statement.

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