A grand jury in the Northern District of California has indicted four defendants, including two officers of the Russian Federal Security Service (FSB), for computer hacking, economic espionage and other criminal offenses, to access Yahoo's network and the contents of webmail accounts.

The defendants are Dmitry Aleksandrovich Dokuchaev, 33, a Russian national and resident; Igor Anatolyevich Sushchin, 43, a Russian national and resident; Alexsey Alexseyevich Belan, aka "Magg," 29, a Russian national and resident; and Karim Baratov, aka "Kay," "Karim Taloverov" and "Karim Akehmet Tokbergenov," 22, a Canadian and Kazakh national and a resident of Canada.

According to the U.S. Department of Justice, the defendants used unauthorized access to Yahoo's systems to steal information from about at least 500 million Yahoo accounts and then used some of that stolen information to obtain unauthorized access to the contents of accounts at Yahoo, Google and other webmail providers, including accounts of Russian journalists, U.S. and Russian government officials and private-sector employees of financial, transportation and other companies. One of the defendants also exploited his access to Yahoo's network for his personal financial gain, by searching Yahoo user communications for credit card and gift card account numbers, redirecting a subset of Yahoo search engine web traffic so he could make commissions and enabling the theft of the contacts of at least 30 million Yahoo accounts to facilitate a spam campaign.

As alleged in the indictment, the conspiracy began at least as early as 2014 and, even though the conspirators lost their access to Yahoo's networks in September 2016, they continued to utilize information stolen from the intrusion up to and including at least December 2016.

The announcement comes as federal authorities investigate Russian interference through hacking in the 2016 presidential election.

Yahoo didn't disclose the 2014 breach until last September when it began notifying at least 500 million users that their email addresses, birth dates, answers to security questions and other personal information may have been stolen. Three months later, Yahoo revealed it had uncovered a separate hack in 2013 affecting about 1 billion accounts, including some that were also hit in 2014.