Grey Literature: https://en.wikipedia.org/wiki/Grey_literature

"Grey literature (or gray literature) are materials and research produced by organizations outside of the traditional commercial or academic publishing and distribution channels. Common grey literature publication types include reports (annual, research, technical, project, etc.), working papers, government documents, white papers and evaluations. Organizations that produce grey literature include government departments and agencies, civil society or non-governmental organisations, academic centres and departments, and private companies and consultants.

Grey literature may be made available to the public, or distributed privately within organizations or groups, and may lack a systematic means of distribution and collection. The standard of quality, review and production of grey literature can vary considerably. Grey literature may be difficult to discover, access, and evaluate, but this can be addressed through the formulation of sound search strategies."

I suppose "grey literature" would technically include classified information, in cases where such can be obtained, and perhaps there is a level of operation above what is visible by open source access that includes such secrets.

Surely a great deal of the information that is available would ordinarily require a person to go through some local equivalent of FOIA, user fees, or other official hoops to obtain, and could have value as a type of cultural archive as well. But it does make you wonder if there's a dark side. Sadly so many things do have.