An FBI investigation of Eric Eoin Marques, deemed "the largest facilitator of child pornography on the planet," has uncovered the world's three largest secret pedophile networks, with potentially millions of users.

The Irish Independent reports that the three sites - Lolita City, The Love Zone, and Pedo Empire - contained large numbers of violent and graphic images, including the rape and torture of children.

The sites cannot be accessed over the internet; users must download and use encryption software before paying for access to the sites.

Marques, 28, is being held in custody in Dublin, where he was arrested, pending the outcome of the extradition request from US authorities. He faces charges of distributing, conspiring to distribute and advertising child pornography. If convicted, he could face up to 30 years behind bars.

After Marques’s arrest, online magazines reported that websites known to be used by pedophiles were shut down by their operators, who suspected spyware had been introduced on their sites by computer hackers believed to be working for US law enforcement. If the sites were infiltrated, the spyware could potentially identify the operators of the sites as well as hundreds of thousands of users.

Underground internet users employing encrypted networks to buy and sell drugs and other illegal goods also began reporting compromised systems merely hours after Marques’s arrest, according to the Irish Independent.

The US and Great Britain have been using "mass surveillance," as revealed by Edward Snowden, to infiltrate and expose the so-called Dark Net, where people use secret programming to hide their identities on the net in order to conduct illicit activities. Online tech magazines have reported that it took US authorities five years to uncover the networks.