Two of the largest dark web marketplaces have been shut down following a “landmark” international law enforcement investigation.
The AlphaBay and Hansa sites had been associated with the trade in illicit items such as drugs, weapons, malware and stolen data.
According to Europol, there were more than 250,000 listings for illegal drugs and toxic chemicals on AlphaBay.
Hansa was seized and covertly monitored for a month before being deactivated.
The agency said it believed the bust would lead to hundreds of new investigations in Europe.
“The capability of drug traffickers and other serious criminals around the world has taken a serious hit today,” said Europol’s executive director Rob Wainwright.
It was a “landmark” operation, according to US Federal Bureau of Investigation (FBI) director Andrew McCabe.
AlphaBay has been offline since early July, fuelling suspicions among users that a law enforcement crackdown had taken place.
‘You cannot hide’
“We know of several Americans who were killed by drugs on AlphaBay,” said US Attorney General Jeff Sessions.
“One victim was just 18 years old when in February she overdosed on a powerful synthetic opioid which she had bought on AlphaBay.”
He also said a 13-year-old boy died after overdosing on a synthetic opioid bought by a high school classmate via the site.
Mr Sessions cautioned criminals from thinking that they could evade prosecution by using the dark web: “You cannot hide,” he said, “We will find you.”
The US Department of Justice (DoJ) said that illegal drugs listed for sale on AlphaBay included heroin and fentanyl.
Investigations were led by the FBI, the US Drug Enforcement Agency (DEA) and the Dutch National Police.
Police in other countries, including the UK, France and Lithuania, also contributed.
The Dutch National Police took over the Hansa marketplace on 20 June after two men in Germany were arrested and servers in Germany, The Netherlands and Lithuania were seized.
This allowed for “the covert monitoring of criminal activities on the platform” until it was eventually shut down a month later.
Ever since AlphaBay went offline earlier in July, users of the site had discussed potential alternative dark web marketplaces on online forums.
Hansa was frequently mentioned, meaning that the authorities were likely able to uncover new criminal activity on Hansa as users migrated to it from AlphaBay.
“We recorded an eight times increase in the number of human users on Hansa immediately following the takedown of AlphaBay,” said Mr Wainwright.