A lifetime ago, I summarized the techniques of sensor detection for a stackoverflow answer, see [1].
The generic answer is every step of the acquisition/storage process can create artifacts worth analyzing statistically: lens defects, color filter array patterns, imaging sensor noise, color filter array interpolation technique, JPEG quantization coefficient varying per camera/manufacturers...
From reading the article, it looks like it talsk about PRNU[0] without really saying it's PRNU. For a while this technique was known (the earliest papers about it are from the early 2000s) but it was computationally complex at the moment, and the domain of a few very knowledgeable persons. A couple[1] of years ago, MobilEdit finally included a decent UI and implementation of the technique into their software[2], which has made it available. However, I'm unsure if the majority of those who use it truly understand what the technique does and what conclusions you can draw from it.
Oh and great summary on SO FrenchyJiby! It's a good intro to those that aren't aware of what can and can't be done in image analysis :)
The generic answer is every step of the acquisition/storage process can create artifacts worth analyzing statistically: lens defects, color filter array patterns, imaging sensor noise, color filter array interpolation technique, JPEG quantization coefficient varying per camera/manufacturers...
[1]: https://stackoverflow.com/a/33674103/4576325