By Ian Bush

PHILADELPHIA (CBS) – Most smartphone users don’t hesitate to tap ‘OK’ when a newly-installed app asks for permission to use certain features on the device. But, a mobile security firm finds some big privacy risks in that practice.

Ads help keep mobile apps free, but the more they know about the smartphone owner, the more valuable they are.

“Smartphones are our most personal devices,” says Derek Halliday, the senior security product manager with Lookout. “They’re with us every day, and they’re collecting really personal information from our contact books, our call logs, our browsing history, but also our actual personal locations.  In a lot of instances, we see that ad networks — in an effort to deliver more relevant, contextual ads to users — are actually tapping into some of this personal information.”

Halliday says the ad networks are doing so by piggybacking on the permissions of the apps they’re delivered with.

Five percent of the free apps analyzed by Lookout had such so-called “aggressive” ads built-in. He estimates more than 80 million apps are affected, “Making this the most pervasive issue that we see in mobile privacy today.”

Halliday says Lookout is pushing for smartphone owners to take the time to check what apps are asking to do with your information, and for ad networks to be upfront and give notice to users before accessing those details.

“We want it to evolve in a way that respects user privacy and security.”