The United States has charged four defendants – including two members of the Russian Federal Security Service, their counterpart to the CIA – in the case of the 2014 mass breach at Yahoo first announced in 2016, the largest such security breach in history .

Canadian police officials and the United Kingdom's MI5 military intelligence service were thanked at the announcement by the Department of Justice Wednesday.

Mary McCord, acting assistant attorney general for the national security division, lamented "the theft of information about at least 500 million Yahoo accounts and the use of that information to obtain the contents of accounts at Yahoo and other email providers."

Dokuchaev and Sushchin "protected, directed, facilitated and paid criminal hackers to collect information through computer intrusions in the United States and elsewhere," McCord said.

McCord alleged the defendants targeted the Yahoo accounts of Russia and U.S. government officials, Russian journalists, and employees of financial services and other commercial entities.

"The criminal charges in the indictment today are allegations, only. And all four defendants are presumed innocent unless and until proven guilty," said Brian Stretch, U.S. Attorney for the Northern District of California, at the announcement. "Silicon Valley is home to the world's leading technology companies. … Everyday, criminal hackers endeavour to gain unauthorized access to personal, proprietary information for nefarious purposes."