Two Russian spies are among four people indicted by the US Department of Justice over the theft of Yahoo user accounts.
Previously, Yahoo said "state-sponsored" hackers were behind the 2014 breach affecting 500 million accounts.
Two members of the FSB, the Russian intelligence agency, conspired with criminal hackers, according to the Department of Justice officials, announcing the charges.
One suspect was arrested on 14 March in Canada.
"The Department of Justice is continuing to send a powerful message that we will not allow individuals, groups, nation states, or a combination of them to compromise the privacy of our citizens, the economic interests of our companies, or the security of our country," said acting attorney general Mary McCord, announcing the charges.
One of the alleged hackers has been one of the FBI's most wanted cyber criminals for more than three years, according to Ms McCord.
"We would hope [Russia] would respect our criminal justice system and respect these charges," she said, acknowledging the fact that the US does not have an extradition treaty with Russia.
"The United Kingdom's MI5 made substantial contributions to the advancement of this investigation," FBI executive assistant director Paul Abbate said.
Yahoo was criticised for the delay in informing users about the 2014 breach.
The stolen data included names, email addresses, telephone numbers, dates of birth and encrypted passwords, but not credit card data, according to Yahoo.
Last year, users were advised to change their passwords.
Around eight million UK accounts were believed to have been affected - including some users of BT and Sky email services.
The suspects were named in a Department of Justice press release as:
- Dmitry Aleksandrovich Dokuchaev, 33, a Russian national and resident
- Igor Anatolyevich Sushchin, 43, a Russian national and resident
- Alexsey Alexseyevich Belan, 29, a Russian national and resident
- Karim Baratov, 22, a Canadian and Kazakh national and a resident of Canada