A Cambridge University graduate has pleaded guilty to 137 charges of online abuse, including child exploitation and encouraging the rape of a four-year-old.
Dr Matthew Falder, 28, admitted to blackmailing victims into sending him severe abuse images of themselves and sharing them on the dark web.
He also admitted to causing the sexual exploitation of a child, voyeurism, making and distributing indecent images of children and encouraging the rape of a four-year-old.
The geophysicist, who worked at Birmingham University until September, degraded and humiliated more than 50 victims online using the names "666devil" and "evilmind".
He had been abusing victims since 2010, until he was arrested on June 21 this year. He has since been held in custody.
Mr Falder, from Edgbaston, Birmingham, posed as a female on sites such as Gumtree to trick his victims into sending him naked or partially-clothed images of themselves.
The disgraced geophysicist then threatened to expose his victims if they did not send severe and depraved abuse images of themselves.
He then distributed the images, including some which showed babies and children being tortured, on the dark web, and discussed them at length to humiliate and degrade the people who were the subject of the pictures.
The case is the National Crime Agency's first in "hurt core" offending - the hidden web forums dedicated to the discussion of and video sharing of "dark" material.
Judge Philip Parker QC remanded Falder into custody until December 7, when he will be sentenced at Birmingham Crown Court.
Ruona Iguyovwe, from the Crown Prosecution Service's International Justice and Organised Crime Division, said: "Matthew Falder is a highly manipulative individual who used his knowledge of computers and the internet to persuade dozens of young people to supply him with degrading images he could distribute online and subsequently use in blackmailing them.
"He clearly enjoyed humiliating his victims and the impact of his offending, which carried on over several years, has been significant."
