Despite Apple's earlier efforts to increase privacy on iOS, mobile ad networks have found new ways to find out what iPhone and iPad users are doing on their mobile devices, according to a new report.
The Wall Street Journal is reporting today, citing sources, that a host of mobile ad networks are now culling data from a unique identifier in the iPhone's wireless networking component, called Open Device Identification Number (ODIN). In addition, the ad networks have taken advantage of OpenUDID, which can be found in the platform's copy-and-paste feature.
Apple made waves in the mobile space last year after telling app developers that they should stop tracking iOS users through the UDID string of characters that uniquely identifies a particular device. The move was designed to increase privacy across Apple's mobile platform, and limit the information developers had been collecting on user behavior.
UDID identification was used frequently for analytics, ad placement in apps, and other behavior-based initiatives on Apple's platform.
Back in March, developers reported that applications they had created that continued to use UDID were being rejected by Apple for entry into the App Store.
"This is a problem," developer Chris Adamson wrote in March, "because we've all had about six months to get off of UDID, and while that's surely enough to get a simple app migrated -- indeed, I have cases where switching it out is a five-line fix -- it is not necessarily the case that everyone can be expected to have already done this."
The UDID restriction quickly became costly for developers and mobile ad networks. In fact, mobile ad server MoPub reported in April that effective CPM in apps on iOS had declined by 24 percent from 76 cents to 58 cents.
According to the Journal, citing conversations with ad networks, they could lose "millions of dollars a week in revenue" if they don't have a viable way to track users.
However, a key component in Apple's decision to stop UDID tracking was preserving user privacy. Critics say that by analyzing a person's UDID, they can find far too much information about them and could eventually personally identify the individual. According to the Journal, privacy advocates it spoke with have the same fear with the use of ODIN.
CNET has contacted Apple for comment on the Journal's report on tracking. We will update this story when we have more information.