FBI investigating Facebook hack as company reveals new information

SAN FRANCISCO (KGO) -- Facebook revealed on Friday that a hack in September affected millions of phone numbers and email addresses.

Facebook said 29 million accounts were involved in the security breach, not 50 million as first thought.

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Facebook plans to send messages to people whose accounts were hacked telling them to what degree their information was exposed.

The company said the FBI is investigating the hack and apparently asked Facebook not to reveal who may be behind the data breach.

RELATED: Here's what Facebook is doing to address major security issue

CNET Executive Editor Ian Sherr joined ABC7's Larry Beil to discuss the hack and what it means for regular Facebook users.

To find out if your account was hacked, visit this Facebook page.