If they are mostly located in China, that might explain why it is difficult to do much about them:
An official Chinese state media outlet recently revealed how illegal paper mills in China are operating to get fake manuscripts published, including in top international journals.
In China, a very high metric for publishing academic papers is required for individuals to get promoted in certain professions or academic fields; but for many people, this indicator is almost out of reach. Thus, a gray industry of scientific ghostwriters has evolved offering a “one-stop service” where submissions and publications are done in the name of the client.
By typing in keywords on Chinese search engines, you can easily find a large number of essay factories.
A reporter from Xinhua Viewpoint, a column of official media Xinhua, posing as a cardiovascular and cerebrovascular physician contacted numerous paper factories and was told that all levels of dissertation could be written and published for him as long as the delivery time was not too short, according to Xinhua in a Jan. 11 report.
Shawn Lin, “Scientific Ghostwriting Factories Booming in China” at Epoch Times (January 23, 2022)
Totalitarianism and science have never been a good mix but if China is the new ruling power, it is the mix we now have.
You may also wish to read: Research Fraud In China: The Weak Spot Of Totalitarianism? (2019)
and
Huge Science Frauds Uncovered In China (2017)