Four people, including two Russian Federal Security Service officers, have been indicted by a San Francisco federal grand jury in connection with a 2014 hacking attack on Yahoo, the U.S. Attorney's Office announced Wednesday.
The indicted FSB agents are Dmitry Dokuchaev, who goes by the alias "Forb", and his superior officer Igor Sushchin.
The indictment says that Dokuchaev and Sushchin paid, directed, and protected two known criminal hackers who took part in the scheme-Alexsey Belan, a Russian national and resident, and Karim Baratov, born in Kazakhstan and a naturalized Canadian citizen and resident. Baratov was arrested in Canada on Tuesday and his case is now pending with Canadian authorities, the Justice Department said. The charges against the four include hacking, wire fraud, trade secret theft and economic espionage.
Both Yahoo and Verizon, which finalised the purchase of the dot-com assets from Yahoo earlier this month, have refused to comment.
The hack in question was only just disclosed by Yahoo past year, although it took place in 2014.
Paul Abbate, head of the FBI's cyber branch, called Yahoo breach "one of the largest cyber intrusions in U.S. history" during a press conference held by the U.S. Department of Justice announcing the indictment.
The individuals are suspected of being involved in the theft of millions of user details through a security breach, including email addresses, dates of birth and hashed passwords, which could be used in more targeted attacks in the future.
The defendants targeted the accounts of Russian and USA government officials, as well as Russian journalists, employers of other providers and employers of financial services.
Russian state security has been blamed for a series of hacks including the high profile attack on the Democratic National Committee during the recent US election.
McCord said the FSB officers' role in the hacking made this crime "much more egregious".
Yahoo disclosed news of an attack in September which had been carried out at some point in late 2014, leading to the loss of 500 million user records. Verizon negotiated a price reduction, trimming $350 million from the acquisition of Yahoo for a total of $4.48 billion. USA authorities have accused the Russian, Iranian and Chinese governments of other cybercrimes, but Wednesday's indictment is the first time a criminal case has been brought against Russian officials.