Senator Al Franken asked software maker Carrier IQ to respond to claims by an independent security researcher that its products collect and transmit potentially sensitive data about millions of mobile phone users.

Carrier IQ makes software that companies including AT&T Inc and Sprint Nextel install in mobile devices. It runs in the background, transmitting data that the software maker says its customers use to better understand their devices and networks, which allows them to improve their service.

Hacking expert Trevor Eckhart last month began publishing research on its functionality, saying it tracks user locations, and this week released a 17-minute YouTube video showing it collect data from an HTC smartphone. A firestorm of criticism has erupted in online forums and on Twitter, where users complained that the software was violating their privacy.

The video shows a piece of software tracking Eckhart as he turns his phone on and off, punches numbers to make a call and records text message in plain text.

The revelation that the locations and other sensitive data of millions of Americans are being secretly recorded and possibly transmitted is deeply troubling, Franken said in a statement. Carrier IQ has a lot of questions to answer.

In his letter, he asked the company for details on the types of data its software collects and what it does with that information.

AT&T and Sprint Nextel both said they use the software in their devices to collect information that helps them improve network and service performance.

We do use carrier IQ, but we do not and cannot look at the contents of messages, etc., as some have speculated, said Sprint spokeswoman Stephanie Vinge-Walsh.

A spokeswoman for Verizon Wireless said that her company did not currently use the software but was not sure if the company had previously been a customer.

Apple Inc said that some devices, including iPhones, that run on its iOS 4 operating system use the Carrier IQ software, but that it does not work with the newer iOS 5. (Reporting by Jim Finkle and Alastair Sharp, additional reporting by Diane Bartz and Poornima Gupta and Tarmo Virki

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