A hacker charged with helping Russian spies breach email accounts pleaded guilty to federal crimes in San Francisco on Tuesday. 

Karim Baratov pleaded guilty to aggravated identity theft and conspiring to commit computer fraud and abuse. Working with agents from the Russian intelligence agency called FSB, Baratov allegedly hacked into email accounts hosted by Google and Yandex. The same agents were also allegedly responsible for the 2014 hack of Yahoo that compromised 500 million user accounts.

Baratov was indicted in February, along with three alleged co-defendants who are based in Russia. Baratov is a Canadian national.

US Attorney Brian Stretch said in a statement that Baratov is "a prolific criminal hacker who had sold his services to Russian government agents." Baratov stood accused of sending phishing emails to specific email accounts, tricking users into handing over their usernames and passwords, and then sending the login information to Russian agents. The breached accounts were hosted by services like Google and Yandex, which is based in Russia, according to the US Department of Justice.

"This prosecution should send a very clear message to hackers around the world that we will identify and pursue charges against individuals who compromise our country's computer infrastructure," Stretch said.

The hackers accused of breaching Yahoo remain at large in Russia, according to the Justice Department.