The U.S. Department of Justice announced Wednesday the indictments of four Russian hackers who were involved in the 2014 hack that resulted in the theft of more than 500 million Yahoo accounts, according to a report from the Washington Post.

The indictments include two members of the Federal Security Service (FSB), the Russian intelligence agency that was once headed by Vladimir Putin, and two criminal hackers hired by the Russians. 

The indicted FSB agents are Dmitry Dokuchaev, who goes by the alias "Forb," and his superior officer Igor Sushchin. Alexsey Belan, one of the most-wanted cyber criminals in the world, and hacker-for-hire Karim Baratov were also charged, according to the Post.

Baratov was arrested in Canada on Tuesday, while Belan is believed to be protected by authorities in Russia. Arrest warrants have been issued for the other three parties.

Read: Who Is Evgeniy Bogachev? Hacker With $3 Million Bounty From FBI May Be Working With Russian Government

The Russian actors will be charged with hacking, wire fraud, trade secret theft and economic espionage, according to officials who spoke to the Washington Post.

The indictments, which are the result of a two-year investigation conducted by the San Francisco branch of the FBI with the help of international law enforcement, will be part of the largest hacking case ever brought by the United States. 

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 charges stem from a hack that took place in 2014, in which more than 500 million Yahoo account credentials were stolen. At the time, it was believed to be one of the largest database breaches in history. Affected users had their Yahoo account, along with associated Flickr, Tumblr and fantasy sports accounts put at risk.

It is still unclear if a 2013 hack that resulted in the theft of more than one billion Yahoo accounts was related to the 2014 hack or carried out by the same or related individuals. Yahoo failed to disclose either attack until 2016, resulting in a considerable cut to the company's sale price in a deal with Verizon.

The charges are unrelated to the 2016 hack of the Democratic National Committee and FBI's ongoing investigation into potential Russian interference that took place during the U.S. presidential election.

According to the indictment, the FSB specifically targeted Yahoo as a means of gathering intelligence information in an attempt to target journalists, political detractors and U.S. government officials. The Russian agents allowed the hackers it worked in partnership with access to the database to use for their own purposes, including spamming and hacking operations that produced financial benefit for both the hackers and the government agents, The Washington Post reported.

The case marks one of the first instances U.S. intelligence has been able to provide evidence that shows the Russian government's reliance on third-party attackers.

"If you illegally target U.S. citizens or American companies, you will be identified and located," Abbate said during a press conference.

It has been a longstanding belief of intelligence agencies that the Russian government has worked with cyber mercenaries to carry out attacks. A recent report from the New York Times suggested a notorious Russian hacker Evgeniy Bogachev worked directly with the Russian government to gather intelligence.