Federal officials have announced the bust of a massive international child porn ring, resulting in the rescue of 23 child victims and the arrest of more than 300 suspects.

Jong Woo Son, 23, a South Korean national, was indicted by a federal grand jury in Washington DC for running the site Welcome To Video, prosecutors announced on Wednesday.

Investigators say that the website, which operated on the encrypted Tor network, was the largest single online depot of child sexual exploitation by volume of content.

An additional 337 site users living in the U.S. and other countries were arrested in the sting.

Welcome to Video, the site used by pedophiles around the world, has now been shut down and replaced with this seizure notice by US and international law enforcement

The arrests were made in multiple countries including the UK, Ireland, South Korea, Germany, Spain, Saudi Arabia, the United Arab Emirates, the Czech Republic and Canada.

Officials said the operation is responsible for the rescue of at least 23 minor victims residing in the U.S., Spain and the UK, who were being actively abused by the users of the site.

'Darknet sites that profit from the sexual exploitation of children are among the most vile and reprehensible forms of criminal behavior,' said Assistant Attorney General Brian A. Benczkowski of the Justice Department's Criminal Division.

In the U.S., the criminal investigative arms of the Internal Revenue Service and Immigration and Customs Enforcement collaborated on the investigation.

According to the indictment, Welcome to Video was launched on the Darknet in June 2015.

Undercover investigators say that the site's upload page had the instruction 'Do not upload adult porn over the age of 15.'

The website's upload page (above) included a message telling users not to upload adult porn

The site hosted more than 200,000 videos of sickening child abuse, including the rape of infants and toddlers, the indictment said.

Users would purchase videos with 'points', which they could earn by uploading new videos, referring new users, or simply paying with bitcoin.

Prosecutors say that Son was the administrator of the site, which raked in some $370,000 in bitcoin payments between 2015 and 2018.

The site's users downloaded child exploitation videos more than one million times in the same time period, according to court documents.

Son is currently serving an 18-month sentence in South Korea, and U.S. authorities are expected to seek his extradition to face justice in America.

How investigators unraveled the child porn plot

Police in the UK found a link to he site on the computer of Matthew Falder, 37

The Welcome To Video site first came to the attention of law enforcement in June 2017, when police in the UK arrested Cambridge graduate Matthew Falder, a geophysicist from an affluent family who led a secret life trading images of child sex abuse.

Falder later admitted 137 offenses, including voyeurism, encouraging child rape, and sharing images showing the abuse of a newborn baby, and has been jailed for 25 years.

The National Crime Agency, Britain's equivalent of the FBI, found a link to the Welcome To Video website on Falder's computer, and launched a joint investigation with authorities in the U.S., Germany and elsewhere.

In the U.S., agents with the IRS and Homeland Security Investigations, a division of ICE, began the meticulous work of tracking the website's operator.

The NCA uncovered Welcome To Video during its investigation into the geophysicist Dr Matthew Falder. His computer is pictured above in an evidence photo

As investigators scrutinized the website's source code, they discovered two occasions where the IP address of the server had not been fully concealed.

Those two IP addresses were traced to a service provider in South Korea, and were registered to an account at Son's address, according to the indictment.

Meanwhile, IRS investigators were also able to track payments made by undercover agents to the Welcome To Video bitcoin account.

The payments were tracked through to a wallet account that Son held with a bitcoin exchange, where he had to register with his name and contact information in order to convert the bitcoin to national currency.

A warrant was issued for Son's arrest by a U.S. federal magistrate judge in February 2018.

On March 5, 2018, agents from the IRS-CI, HSI, the UK's NCA, and Korean National Police in South Korea arrested Son and seized the server used to operate Welcome To Video.

Using a sophisticated analysis of bitcoin transactions, which are recorded on the public blockchain, the investigators were also able to backtrace many of the payments to the website, and unmask its users.

The website (above) sold download privileges for bitcoin, which allowed IRS investigators to trace the transactions on the blockchain to wallet accounts registered to Son

Hundreds of arrests followed around the world in the following months.

Two users of the Darknet market committed suicide subsequent to the execution of search warrants.

The operation resulted in the seizure of approximately eight terabytes of child sexual exploitation videos, which is one of the largest seizures of its kind, officials said.

The files included over 250,000 unique videos, and 45 percent of the videos contain new images that have not been previously known to law enforcement.

Analysis of the files led to identification of some of the abused children, 23 of whom have been located and rescued so far.

The National Center for Missing and Exploited Children is currently in the process of analyzing thousands more videos, in hope of identifying and rescuing the child victims they depict.