Re: Any suggestions how to check these
Not easily. You're best off installing some kind of checker, and Checkpoint's essentially just touting for business with this report, but basically, you're going to have to educate your son about the dangers of installing just any old shit; you know a "don't go with strangers" talk. Note, it's not just games, anything that promises something for nothing is likely to be suspicious.
BTW. 150 million sounds a lot but given the installed base, and the way the numbers were calculated, it's not that significant. Checkpoint has form in the area and regularly releases reports like this.