Apple has removed 17 mobile apps from its App Store after a security vendor reported them as infected with malware.
But an unknown number of people who downloaded the free apps continue to be at risk of having their devices being used to quietly carry out ad-fraud related tasks such as continuously clicking on links or opening Web pages without any action on their part.
In a report Thursday, Wandera described the 17 malicious apps it found as containing clicker Trojan malware designed to generate revenues for their developer by fraudulently inflating traffic on pay-per-click websites. An attacker can also use such malware to drain the budgets of rival websites by artificially inflating the amount they owe to an ad network, Wandera said.
The apps were found receiving instructions from a known command-and-control server. Commands from the C2 server included those that could silently load websites, deliver targeted advertising, remotely reconfigure infected devices, and sign up users for expensive services without their knowledge.
The list of infected free apps, which Wandera has published on its website, included productivity, travel, platform utility, restaurant finder, and video-editing apps from India-based AppAspect Technologies. The developer currently appears to have at least 51 apps on Apple's App Store, of which 35 are free.
Michael Covington, vice president of product at Wandera, says the company only tested the free apps. So it is unclear if AppAspect's paid products are similarly infected.
Apple, unlike Google, does not provide any information on download numbers for apps on App Store. As a result, it's hard to determine with any certainty how many people might have downloaded the infected AppAspect software, Covington says. But based on how the India-based developer's Android versions of the same apps have performed, it is safe to assume that a significant number of iOS users have been impacted, he notes.
Wandera discovered nine AppAspect apps for Android on Google's Play Store that are counterparts of the iOS versions. Those apps have nearly 1.1 million installs in total. "Because the developer seems to have spent more time developing on the Apple App Store — with 51 apps on the App Store versus 28 on Google Play — we assume their iOS apps reach even more users," Covington says.
None of the 28 Android apps that AppAspect has on Google's Play Store currently appear infected. However, some of the apps were previously reported as malicious and removed. The developer appears to have uploaded the again to Play without the malware, Wandera said.
Bypassing Security Controls
Both Apple and Google have implemented substantial measures over the years to quickly identify and remove rogue apps from their mobile app stores. Their respective stores continue to be by far the safest location for users to download Android and iOS apps. But the sheer volume of apps being uploaded to these stores and the ingenuity of some developers has resulted in malicious apps frequently getting uploaded anyway.
In Apple's case, the company's app review process is designed more to ensure that iOS apps meet optimal usability and performance standards, Covington says.
Apple also verifies that developer's API calls as intentioned and often rejects developers that violate the company's rules for how an app should run.
"We believe these [AppAspect] apps bypassed the Apple vetting process because the Trojan developer didn't put any "bad" code directly into the app," Covington notes. "Instead, the [apps were] configured to obtain commands and additional payloads directly from the C&C server, which is outside of Apple's review purview."
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