Yahoo has fallen victim to the largest cyber breach in history and Russian state-sponsored cyberspies are apparently to blame.

The attack occurred in 2014 and compromised sensitive personal details, including encrypted passwords, of more than 500 million Yahoo users worldwide. Yahoo reveled the data stolen included names, encrypted passwords, email addresses, telephone numbers and dates of birth.

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"This is the biggest data breach ever," said Bruce Schneier, a well-known American cryptographer, computer security and privacy specialist who wrote several books on computer security and cryptography.

The data breach is the largest from a single site in history, according to a database of hack attacks compiled by the Privacy Rights Clearinghouse, a California-based non-profit that also seeks to raise consumers' awareness of how technology affects personal privacy.

Schneier said it was too early to say what impact the breach might have on Yahoo and its users because many questions remain, including the identity of the state-sponsored hackers behind it. Despite his misgivings, three unidentified U.S. intelligence officials were quoted by media as saying they're convinced the attack was a Russian state-sponsored hack because of its resemblance to previous hacks traced to Russian intelligence agencies or hackers under their command.

The Yahoo breach was brought to light when technology news site Motherboard reported last August that a cyber criminal using the moniker Peace was selling the data of 200 million Yahoo users for just $1,800. Peace previously claimed responsibility for the hack.

Peace also previously attempted to sell on a hacker forum information allegedly belonging to hundreds of millions of accounts at MySpace and LinkedIn, including names, passwords and email addresses.

Peace is believed to be the alias for a group of Russian hackers and isn't a lone individual. In 2014, Russian hackers stole the personal data of 1.2 billion users. This data, however, was stolen from hundreds of thousands of sites and combined into a single collection.

TagsYahoo, largest cyber breach in history, Russian hackers, encrypted passwords, Bruce Schneier, Privacy Rights Clearinghouse, Peace