A widespread ad fraud operation, nicknamed “SlopAds,” has been stopped. The campaign was discovered by HUMAN’s Satori Threat Intelligence team and involved 224 malicious applications on the Google Play Store that were downloaded more than 38 million times. These apps used sophisticated methods like obfuscation and steganography to evade detection by Google’s security tools. The operation was globally massive, with ad traffic reaching 2.3 billion bid requests every single day. The highest volume of ad impressions came from the United States, which accounted for 30% of the traffic, followed by India and Brazil.
The researchers who uncovered the operation named it “SlopAds” because the apps appeared to be mass-produced, similar to what is known as “AI slop,” which also referenced a variety of AI-themed apps and services found on the threat actors’ command-and-control server. The SlopAds ad fraud campaign used various evasion tactics to get around Google’s app review process and other security software.
These malicious apps were designed to behave differently depending on how a user installed them. If a user installed an app naturally from the Play Store without clicking on one of the campaign’s ads, it would function normally. However, if the app detected that it was installed through one of the threat actors’ ad campaigns, it would use Firebase Remote Config to download an encrypted configuration file. This file contained URLs for the ad fraud malware module, cashout servers, and a JavaScript payload.
Once the app had this file, it would then perform a series of checks to ensure it was running on a real user’s device and not being analyzed by a security researcher or software. This was a crucial step in their plan to avoid detection.
If the app passed these checks, it would download four separate PNG images. These images were not what they seemed; they used steganography to conceal parts of a malicious APK, or Android application package, that was the core of the ad fraud campaign.
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