Hundreds of iOS applications have been pulled out of the App Store, following a report from analytics service SourceDNA, which uncovered a group of applications that were extracting users’ personally identifiable information, including email addresses associated with their Apple IDs, devices and peripheral serial numbers, as well as a list of apps installed on their phone. The applications in question had been using an SDK from a Chinese advertising company called Youmi which was accessing this information by way of private APIs, the report found.
Nearly all of the developers were located in China so, for now, this appears to be an isolated incident. However, the larger concern here has to do with how long this activity had been taking place – and what that means in terms of Apple’s App Store review process, given that it hadn’t caught this suspect activity until being alerted to it by a third party.
According to SourceDNA, Youmi had apparently been experimenting with what sort of information it could pull from users’ devices for some time. Nearly two years ago, for example, the firm began obfuscating a call to get the frontmost (currently running) app’s name – seemingly a small test of what it could sneak into the App Store. And when it realized that it was able to get this through Apple’s App Review process, it then began to use the same obfuscation technique to request other data, including the advertising ID.
The ad ID can be accessed for tracking ad clicks, but given that Youmi was surreptitiously collecting it, the firm may have been using it for other purposes, the report speculates.
In addition, SourceDNA noted that while Apple had been locking down private APIs in order to prevent apps from reading the platform serial number in iOS 8, Youmi worked around this by enumerating peripheral devices, like the battery system. It would then send those serial numbers as the hardware identifier.
SourceDNA, which helps app developers improve their code and address security flaws, says it found what Youmi was up to when it was updating its Searchlight product to check for use of private APIs – something that should get developers’ apps banned from the App Store. Surprisingly, it actually found quite a few apps that had gotten through.
In total, SourceDNA came across 256 apps with an estimated total of 1 million downloads that had been using a version of the Youmi SDK that was violating user privacy. However, the company adds it’s possible that the developers themselves didn’t realize what the SDK was doing, as the user data is uploaded to Youmi’s server.
What’s more concerning here is the implication of SourceDNA’s findings. The obfuscation method is fairly simple, the company says, and the apps have been using it for a long period of time. In fact, SourceDNA’s founder Nate Lawson tells us this has been going on for about a year-and-a-half.
“We’re concerned other published apps may be using different but related approaches to hide their malicious behavior,” a SourceDNA blog post states. “We’re continuing to add new features to our engine to discover anomalous behavior in app code and find out if this is the case.”
SourceDNA submitted its report to Apple, and Apple replied by offering the company a statement (see below) indicating the apps in question had been banned. Apple says it’s now working with developers who were using Youmi’s SDK to get their apps updated to be in compliance with Apple’s guidelines so they can return to the App Store.
“We’ve identified a group of apps that are using a third-party advertising SDK, developed by Youmi, a mobile advertising provider, that uses private APIs to gather private information, such as user email addresses and device identifiers, and route data to its company server. This is a violation of our security and privacy guidelines. The apps using Youmi’s SDK have been removed from the App Store and any new apps submitted to the App Store using this SDK will be rejected. We are working closely with developers to help them get updated versions of their apps that are safe for customers and in compliance with our guidelines back in the App Store quickly.”