The two agencies say they are responding to the growing amount of personal information held in smartphones and a recent rise in the attacks on the security of that information.
The FCC has sent letters to AT&T, Verizon, T-Mobile, Sprint, and U.S. Cellular asking for information on their processes for reviewing and releasing security updates for mobile devices. The FTC has asked for similar information from Apple, Blackberry, Google, HTC, LG, Microsoft, Motorola, and Samsung.
The companies, which control the vast majority of mobile contracts and smartphone handsets sold in the U.S., have 45 days to respond, at which time the two agencies will analyze the responses and share data with each other.
The inquiries haven't risen to the level of a formal investigation or rulemaking, but they could depending on what is discovered.
"We're attempting to get an assessment on the state of what carriers do to push out patches for device vulnerabilities, how quickly they do it, and what are some of the barriers and challenges they have," said Neil Grace, a spokesman for the FCC.
As part of its inquiry, the FTC is asking for information about when device makers learn of vulnerabilities from software and chip vendors and when or if they issue security updates.
Because cellular carriers customize the software on their devices, it's often not possible for operating system vendors like Google to push updates directly to consumers. The updates have to be submitted to carriers and then work through the carrier's own control process before being released.
Part of the motivation for the inquiry was the Stagefright vulnerability that hit hundreds of millions of Android phones last year. Stagefright left phones vulnerable if a user clicked on a specially formatted MMS message.
Google provided a fix but had to wait until cellular carriers pushed the update to customers. On older phones, some consumers might not have received the update at all.