It said that more than 40 apps used the library which had been downloaded more than six million times.
The library in question supports Android 2.3 through to Android 6 and devices from Samsung, Huawei, Meizu, Mi and Nexus.
Sophos said the primary function of the library was to keep the adware alive even if the user tried to force it to close or scrub the memory.
Sophos gave the following list of package names:
It said that once an app that contained the library was installed, ads would start to pop up. Even if the ad was force stopped from the system settings, the pop-ups would continue.
Sophos provided screenshots of ads popping up in an app called Snap Pic Collage Color Splash (seen above, right) which it said had been downloaded from Google Play more than 50,000 times.
It said it would continue working with Google to get the adware removed.