Researchers from security firm White Ops discovered several Android apps in the official Play Store that installed a hidden browser to load pages containing ad and commit ad fraud.
The company shared its findings with Google which has quickly removed an undisclosed number of Android apps from the Google Play Store.
According to Google, the apps were part of an ad fraud botnet tracked as Terracotta.
The White Ops Satori Threat Intelligence & Research team has been actively tracking the Terracotta botnet since late 2019.
Terracotta operators uploaded apps on the Google Play Store, they promised users free goods (i.e. coupons, shoes, tickets) if they installed the applications on their devices.
“The TERRACOTTA malware offered Android users free goods in exchange for downloading the app—including shoes, coupons, and concert tickets—which users never received.” reads the report published by WhiteOps. “Once the app was installed and the malware activated, the malware used the device to generate non-human advertising impressions purporting to be ads shown in legitimate Android apps.”
In a single week in June 2020, the campaign generated more than two billion fraudulent bid requests, the malware has infected upwards of 65,000 devices, and spoofed more than 5,000 apps.
Users were tricked into waiting two weeks before receiving the free products, while the app installed on their devices was operating in the background.
The malicious apps downloaded and executed a modified version of WebView browser in stealth way. The browser was used to perform ad fraud by loading ads and gaining revenue from non-human generated advertising impressions.
According to WhiteOps researchers, the Terracotta botnet used advanced techniques to avoid detection.
Experts pointed out that Google has removed multiple apps from the Play Store, but some devices still appearing to be infected. Google also disabled malicious apps on all users’ devices.
“Due to our collaboration with White Ops investigating the TERRACOTTA ad fraud operation, their critical findings helped us connect the case to a previously-found set of mobile apps and to identify additional bad apps. This allowed us to move quickly to protect users, advertisers and the broader ecosystem – when we determine policy violations, we take action,” a Google spokesperson said.
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(SecurityAffairs – hacking, Terracotta)