Understanding how your fitness tracker uses your personal data

Activity trackers like Fitbit and Jawbone are a fitness craze taking wrists by storm.

“It's amazing how you don't really notice how many steps you're taking a day and this thing helps you so much more to try to get there,” said Tim Grogan of Northern Kentucky, who got his Fitbit for Christmas.

The wrist fitness trackers measure your every step and can help you keep track of much more.

“What you're eating, when you're eating, how much sleep, how much water - you can track all of that too,” said JD Marcum owner of Crossfit Y'all in Erlanger.

Then, using the fitness trackers, you can take that information and record it on your smartphone or tablet.

But experts say there could be a downside to sharing your fitness feats and calorie counting that many haven't considered.

“Semantech, a major security software vendor, has done a study and said somebody could potentially hack into Fitbit and someone could potentially hack your device and get much more detailed information,” said FOX19 NOW Tech Expert Dave Hatter.

Last year, Sen. Chuck Schumer (D-N.Y.) warned that activity trackers are a privacy nightmare waiting to happen. Since then, Fitbit amended its privacy policy saying your personal information won't be shared unless legally necessary or unless you give consent.

But companies can still share what they call "de-identified," or aggregate, data. Experts say the problem with aggregate data is that it can be traced right back to you.

"Simply by looking at the data can find out with pretty good accuracy what your gender is, whether you are tall or short, whether you are heavy or light. But what's really interesting is you can 100 percent be identified by your gait,” said former CIA Chief Technology Officer Ira “Gus” Hunt.

When speaking to a conference of tech experts, Hunt warned our health information could be a target for terrorists.

“This is something you have to worry about you think about cyber threats as they emerge. It's not just going to be your business (that they're attacking). Ultimately it's going to be about your health. Things are going to be at risk if you're not careful,” said Hunt.

And experts say even more potentially dangerous than the activity trackers are fitness apps like “mapmyrun,” which log your running routes, even showing how often you run them.

It's the potential side effect of a healthy life if it's all recorded online.

“The genie is out of the bottle at that point. If you don't want it out there, don't put it out there. That's the only way to have any kind of privacy or protection at this point,” said Hatter.

This information is also being used in courtrooms. There's an Ohio case where someone claimed a disability but was logging three-mile runs each day.

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