US law enforcement has charged three men believed to have been behind "the largest data breach in US history".
The US Department of Justice (DoJ) reported charging Vietnamese citizens Viet Quoc Nguyen, 28, and Giang Hoang Vu, 25, and Canadian citizen David-Manuel Santos Da Silva, 33.
The charges allege that Nguyen hacked into and stole confidential information from at least eight US email service providers between February 2009 and June 2012.
The information included over one billion email addresses from the companies' marketing departments, and was listed by the DoJ during a Congressional inquiry in June 2011 as the largest data breach in US history.
Vu reportedly helped Nguyen use the stolen information to send "tens of millions" of malicious spam messages.
Da Silva, who was also indicted by a federal grand jury on 4 March 2015 for conspiracy to commit money laundering, reportedly helped Nguyen and Vu to monetise the scheme and hide incoming revenue.
Vu was arrested by Dutch law enforcement in 2012 and extradited to the US in March 2014. He pleaded guilty to conspiracy to commit computer fraud in February and is scheduled to be sentenced on 21 April.
Da Silva was arrested at Fort Lauderdale-Hollywood International Airport on 12 February, and is scheduled to be arraigned on 9 March in Atlanta. Nguyen remains at large.
US assistant attorney general Leslie R. Caldwell listed the charges as a major step in bringing "international" cyber criminals to justice.
"These men, operating from Vietnam, the Netherlands, and Canada, are accused of carrying out the largest data breach of names and email addresses in the history of the internet," said Caldwell.
"The defendants allegedly made millions of dollars by stealing over a billion email addresses from email service providers. This case again demonstrates the resolve of the DoJ to bring accused cyber hackers from overseas to face justice in the US."
Reginald Moore, special agent in charge of the US Secret Service Atlanta Field Office, explained that the charges prove the need for increased collaboration between departments when combating cybercrime.
"Our success in this case and other similar investigations is a result of our close work with our law enforcement partners," he said.
"The Secret Service worked closely with the DoJ and the FBI to share information and resources that ultimately brought these cyber criminals to justice.
"This case demonstrates that there is no such thing as anonymity for those engaging in data theft and fraudulent schemes."
The charges have been welcomed by members of the security community. Imperva CTO Amichai Shulman said he expects the move to set off alarm bells in cybercrime circles.
"I think the most important lesson here is that law enforcement agencies are able to point out specific individuals involved in specific acts of cybercrime even when they are in distant locations around the globe," he said.
"My belief is that, if enough resources are put up against small breaches as well as large breaches in a ‘zero tolerance' policy against cyber violation, we'd see the number of attacks decrease significantly over a short period of time."
Mark James, security specialist at ESET, hopes to see similar operations in the near future.
"Hopefully this will turn out to be a success and will go on to many more cases showing that the fight against cybercrime is not always a losing battle," he said.
The latest developments come during a global push by law enforcement to combat cyber crime.
The UK National Crime Agency arrested 57 people on 6 March accused of cyber offences as a part of a nationwide operation.
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