"Materia Reservada" (Reserved Matter) is a book written by Spanish journalist and ufologist, JJ Benítez. The book, first published in 1992, is a comprehensive analysis of the UFO phenomenon, delving into the author's investigative experiences and encounters with alleged extraterrestrial life. The book's popularity has led to numerous requests for a PDF download, with many seeking to access the content online.

Benítez alleges that the release of files was a "smoke screen" designed to hide more sensitive data.