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MIAMI (CBSMiami) — The U.S. has charged Russian Federal Security officers with hacking Yahoo along with millions of email accounts in what is being called one of the largest data breaches in U.S. history.

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A grand jury on Wednesday indicted four people, two of which are Russian Federal Security Service (FSB) officers, with computer hacking and economic espionage among other charges connected to the conspiracy that started in January 2014.

The FSB is considered a law enforcement agency and a successor of the Soviet Union’s KGB. Acting Assistant Attorney General McCord explained the unit the officers were from is also the FBI’s point of contact in Moscow for cyber-crimes.

The Justice Department said the group gained access to Yahoo’s systems to steal information from at least 500 million Yahoo accounts and then used that information to get content from other accounts on Google and other webmail providers.

Accounts hacked include those of Russian journalists, government officials in the U.S. and Russia and employees in the private sectors of finance and transportation, among other.

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The Justice Department identified the officers as Dmitry Dokuchaev and Igor Sushchin and the hackers as Alexsey Belan and Karim Baratov.  Baratov was arrested on Tuesday in Canada but Belan remains on the loose and is known to law enforcement.

“Belan has been indicted twice before in the United States for three intrusions into e-commerce companies that victimized millions of customers, and he has been one of the FBI’s most wanted cyber criminals for more than three years. Belan’s notorious criminal conduct and a pending Interpol Red Notice did not stop the FSB officers who, instead of detaining him, used him to break into Yahoo’s networks,” said McCord.

Department officials said Belan also lined his pockets in the crime, stealing financial information like credit card numbers from users’ email accounts.

“He also gained access to more than 30 million Yahoo accounts, whose contacts were then stolen to facilitate an email spam scheme,” said McCord.

Attorney General Jeff Sessions made the announcement on Wednesday, calling it one of the largest breaches in the nation’s history.

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“Cybercrime poses a significant threat to our nation’s security and prosperity, and this is one of the largest data breaches in history,” said Sessions.