"Cheaper phones tend to use the Android Open Source Platform (AOSP) and come with anywhere between 100 and 400 pre-installed apps – all it takes is infecting one of them." 100-400 pre-installed apps? That's crazy.
Considering every single Android phone "uses" AOSP, I have a hard time taking this article seriously as more than simply fear mongering for Trend Micro. Yes, many low-end cheap devices come with malware and should be used with caution, but 400 extra "apps"? I'd love to see the data, cause I think not.
AOSP is Android without the google botnet stuff. If you are using an Android device that has play store it's got google's frameworks and apps running on top of AOSP.
Think of AOSP like chromium, and your typical android firmware like Chrome.