A man once described by an FBI agent as the world’s largest “facilitator” of child abuse websites pleaded guilty on Thursday to operating a web hosting service that allowed users to anonymously access hundreds of thousands of images and videos depicting child abuse.

Eric Eoin Marques, 34, faces a mandatory minimum of 15 years in prison and a maximum of 30 years after his guilty plea to one count of conspiracy to advertise child abuse images. A plea agreement will ask the US district judge Theodore Chuang in Maryland to sentence Marques to 15 to 21 years in prison, but the judge is not bound by the recommendation.

Marques can withdraw his guilty plea if the judge departs from that recommended range. Chuang is scheduled to sentence Marques on 11 May.

Marques, who spent years fighting his extradition from Ireland to the US, operated a web hosting service on the darknet that allowed thousands of users to view and share child abuse images, according to a court filing on Thursday.

Marques, a dual citizen of the US and Ireland, has remained in custody since his August 2013 arrest in Dublin after an extradition request from the US. He was living in Ireland at the time of the alleged offenses. The server that he allegedly used was in France.

Marques was extradited from Ireland to Maryland last year. The plea agreement does not give him credit for the nearly six years he spent in custody in Ireland.

The darknet is part of the internet but hosted within an encrypted network. It is accessible only through anonymity-providing tools, such as the Tor browser.

Marques created and operated a free, anonymous web hosting service, called Freedom Hosting, on a network allowing users to access websites without revealing their IP addresses. In 2013, FBI agents in Maryland connected to the network and accessed a child abuse bulletin board with more than 7,700 members and more than 22,000 posts. Agents downloaded more than 1 million files from another website on the network, nearly all of which depicted sexually explicit images of children. Images on the service depicted the rape and torture of infants and older children.

“Did you do the things the government said you did?” the judge asked Marques after a prosecutor read aloud a summary of the case against him.

“Yes,” Marques said.

Authorities seized nearly $155,000 in US currency from Marques, who said during an August 2013 extradition hearing that his business had been “very successful” and profitable, according to Thursday’s court filing.

Marques was indicted in April 2019 in Greenbelt, Maryland, on four counts: conspiring to advertise child abuse images, conspiring to distribute child abuse images, advertising child abuse images and distribution of child abuse images.

The FBI special agent Brooke Donahue has described Marques as “the largest facilitator of child pornography websites on the planet”, according to court records. Donahue also testified that Marques had been searching online for information about obtaining a Russian visa and citizenship, the Irish broadcaster RTE reported.

“He was trying to look for a place to reside to make it most difficult to be extradited to the United States,“ the FBI agent said.

Irish authorities didn’t charge him with any related crimes while he fought his extradition.

“That decision was made notwithstanding that [Marques] had offered to plead guilty to at least some of the potential charges that might have been brought against him in Ireland,” a justice on the supreme court of Ireland wrote in a March 2019 judgment rejecting his final appeal.

Hurson said Marques has “zero ties” to the US and hopes to leave the country as soon as he completes his sentence.