A pair of Android barcode reader apps that were downloaded more than 1 million times were found to contain ad fraud malware that tries to stay hidden by generating advertisements that instantly disappear from view.
The malware, detected as AndroidOS_HiddenAd.HRXJA, can operate in the background even when infected devices aren't actively being used, and it attempts to confuse victims as to the source of the infection by disguising itself as other apps.
In a recent company blog post, Trend Micro mobile threats analyst Jessie Huang names the offending apps as "Barcode Reader" and "QR & Barcode Scanner." (Trend Micro did not reveal the publisher names.) Huang notes that Google removed the apps from the Google Play Store upon being informed of the scam.
Trend Micro says that in the course of its research, it actually identified samples of 51 different apps that demonstrated the same adware behavior; however, Google had either already removed these other apps, or they were distributed through other online marketplaces or websites.
While the barcode apps do function as advertised, they also run a malicious background service that's disguised under a package name that falsely impersonates another legitimate app (e.g. com.facebook), the blog post states. As a further attempt to shift the blame elsewhere, the app makes it so that if users review a list of recent tasks on the phone, they will see the name and icon of other apps already stalled on the phone.
Using a timer, this service shows an advertisement every 15 minutes. The ad immediately closes upon opening, so the user only sees a brief flash, which may not arouse suspicion. However, that's long enough for a false ad impression to be registered.
This behavior is controller via a malicious server, which sends the apps configuration information, ad IDs and other commands. "It may open specified content in the phone’s browser or start an activity with the FLAG_ACTIVITY_NEW_TASK intent. If any activity is started this way, the user won’t know which app opened the new activity," Huang writes.
In a separate blog post, Trend Micro also reported that it found a variant of the Tekya ad fraud family in five malicious apps that had been sneaked into, and later removed from, the Google Play Store. Researchers from Check Point Software Technologies had previously reported on Tekya malware found on children's games and utilities apps made available via Google Play.