you can check this yourself here: http://z-lib.org
I do not think these people are cybercriminals. They are the best we got to help information preservation (next to the Internet Archive) in the 21st century.
The fact they had to mention that these people are Russian also strikes me as odd. They don't even seem to be government affiliated, I'm pretty sure the FBI would've said so if there was even a slight hint of that.
While OpenAI can freely use all copyrighted material and make billions off of it, these people giving it out for free are supposed “criminals”. Aaron Schwartz didn't die for this.
@ErikUden In the spirit of "piracy is curation", folks may want to know that Z Library has a lot of domain redundancy and that there is a reddit forum that usually has pretty good information about which ones are currently working.
https://www.reddit.com/r/zlibrary/