‘As with many hidden criminal syndicates, you don’t always know what’s happening,’ says Retraction Watch’s Ivan Oransky about paper mills. They are the biggest organised fraud perpetrated on scientific journals ever, eroding scientists’ trust in the publishing system – and in each other.

While plagiarism and fraud isn’t new – individual researchers have been caught photoshopping electron microscopy images or inventing elemental analysis data – paper mills serve up professional fakery for their customers on an industrial scale. Buyers can apparently purchase a paper, or authorship of one, on any topic based on phony results to submit to a journal. This makes them not only harder to detect and crack down on, but also exponentially increases the damage they could do.

The extent of their operations became apparent in early 2020. Two independent groups of image detectives came across a number of manuscripts, all from different authors at different institutions working on different biomedical topics, that seemed to share strange inconsistencies – as if they had all used the same stock images. The set now contains almost 600 manuscripts. Another set of 125 was discovered only a few months later. And there could be 10 times as many professionally manipulated papers that have not yet been – and might never be – found, estimates science integrity consultant Elisabeth Bik.