Earlier this week, forensic expert Jonathan Zdziarski attracted attention for his disclosures of what appeared to be “backdoors” in iOS that could allow for covert data collection of users’ information from their devices. While Apple issued a statement denying that anything nefarious was involved, the company has now posted a new support document (via Cabel Sasser) offering a limited description of the three services highlighted in Zdziarski’s talk.
Each of these diagnostic capabilities requires the user to have unlocked their device and agreed to trust another computer. Any data transmitted between the iOS device and trusted computer is encrypted with keys not shared with Apple. For users who have enabled iTunes Wi-Fi Sync on a trusted computer, these services may also be accessed wirelessly by that computer.
The three processes include: 
– com.apple.mobile.pcapd: Diagnostic packet capture to a trusted computer, used for diagnosing app issues and enterprise VPN connection problems.
– com.apple.mobile.file_relay: Used on internal devices and can be accessed (with user permission) by AppleCare for diagnostic purposes on the user’s device.
– com.apple.mobile.house_arrest: Used by iTunes for document transfer and by Xcode during app development and testing.
Security experts will undoubtedly have additional questions about just how these services work and whether there are better and more secure ways of accomplishing the tasks they handle. At the very least, however, today’s disclosure demonstrates a willingness by Apple to share information about the legitimate need for these services and should help quell unsupported speculation that Apple has worked with security agencies to implement these tools to allow for covert surveillance.