Russian government spies were behind Yahoo Inc.’s notorious 2014 security breach, stealing information about more than a half billion online accounts, including those used by U.S. military officials and by employees of firms in banking, finance and transportation, federal authorities said Wednesday.

The Justice Department announced the indictments of Dmitry Aleksandrovich Dokuchaev and Igor Anatolyevich Sushchin, officers of Russia’s Federal Security Service, known as the FSB, alleging they directed and paid for the illegal collection of information in the U.S. and abroad. It is the first such criminal case to directly target Russia.

The case is expected to escalate tensions between the U.S. and Russia over cybercrime and espionage. Congress and federal investigators are probing what U.S. intelligence agencies have described as aggressive efforts by Russia to influence the 2016 election, which it has denied.

The House Intelligence Committee has a hearing next week on the matter, with scheduled appearances by James Comey, director of the Federal Bureau of Investigation, and James Clapper, former Director of National Intelligence.

Authorities said the two Russian agents worked with indicted co-conspirators Alexsey Belan and Karim Baratov to hack into Yahoo computer systems, starting in January 2014. They gained access to the content of 6,500 accounts and used information stolen from Yahoo to target other email providers, including Google.

Source: Two Russian Spies Charged in Massive Yahoo Hack