Yahoo says the indictments against four Russian nationals, two with direct ties to that country’s Federal Security Service (FSB), involved in the multiple cyberattacks against company prove that the incursions were state-sponsored.

On Wednesday, the U.S. Department of Justice announced it has charged the four — 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 — with computer hacking, economic espionage, and other criminal offenses in connection with a conspiracy going as far back as January 2014.

Last year, Yahoo revealed it was the victim of at least two hacking incidents from an “unauthorized third party.” The first resulted in 500 million accounts compromised, while the second saw 1 billion accounts affected. What was more surprising was that these attacks happened between 2013 and 2014 as a result of cookies forged by hackers who had obtained Yahoo’s proprietary code.

The Department of Justice alleges that some of the accounts targeted were of “predictable interest” to the FSB, including those belonging to Russian journalists, Russian and U.S. government officials, employees of a “prominent Russian cybersecurity company,” and employees of other providers. Others targeted include those belonging to employees of a Russian investment banking firm, a French transportation company, U.S. financial services and private equity firms, a Swiss bitcoin wallet, a banking firm, and a U.S. airline.

Each defendant faces multiple counts, each with lengthy prison terms. While all face at least 10 years for conspiracy to commit computer fraud and abuse, Belan, Dokuchaev, and Sushchin could receive harsher prison terms if convicted. However, because they are Russian nationals, it’s unclear whether they’ll actually be brought to trial. But today’s announcement is good news for Yahoo because it offers proof of state-sponsored cyberattacks.

“Identification of individual Russian hackers [is] largely symbolic, but significant nonetheless. There’s probably little likelihood that the identified hackers will ever face justice in the United States. The U.S. has no extradition treaty with Russia. Today’s disclosure by the department of justice is nonetheless very significant for a number of reasons,” remarked Robert Cattanach, a partner at the law firm of Dorsey & Whitney who was previously a U.S. attorney.

In a statement, Yahoo’s assistant general counsel and head of global law enforcement, security, and safety Chris Madsen wrote: “We appreciate the FBI’s diligent investigative work and the DOJ’s decisive action to bring to justice those responsible for the crimes against Yahoo and its users. We’re committed to keeping our users and our platforms secure and will continue to engage with law enforcement to combat cybercrime.”

Today’s announcement perhaps closes the loop on a big blemish on Yahoo’s efforts to close an acquisition deal with Verizon. The telecommunications company is in the process of purchasing Yahoo’s core assets for $4.8 billion, but because of the two previously undisclosed incidents, Verizon will receive a $350 million discount on the deal.