[naftaliharris]

It's pretty surprising students think they can get away with this. If there's any class you'd get caught in, it'd be a CS class. In the CS classes I took in undergrad and grad school, the professors would tell everyone they would be using automated plagiarism detectors, and even explain a bit about how they worked and explicitly say they were smart enough to detect the "rename-the-variables" trick.

That said, I've got to imagine that claims that "as many as 20 percent of the students in one 2015 computer science course were flagged for possible cheating" are a misrepresentation or a misunderstanding, on the part of the journalist. I mean, sure, if you set the threshold for the plagiarism detector at a low level, you can flag 20%, 50%, or however many students you want for "possible cheating", but it's not necessarily a real thing.