As part of an apparent coordinated distributed denial of service (DDos) attack on multiple popular websites this morning, many Facebook users were unable to access the site for a period of a few hours. The source of the attack, which also took down Twitter for hours and struck LiveJournal as well, has not yet been discovered. However, Facebook says service has been restored for most users and no user data was at risk:

Facebook has been known for having a very strong performance record overall, but today’s attack seems to have been coordinated and large enough to affect multiple big sites. Twitter was down for about 2 hours and is still defending against some attacks.

Update: According to Facebook’s chief security officer Max Kelly, the attacks were targeted at an individual known as “Cyxymu,” a blogger in the Republic of Georgia, CNET reports:

“It was a simultaneous attack across a number of properties targeting him to keep his voice from being heard,” Kelly said. “We’re actively investigating the source of the attacks and we hope to be able to find out the individuals involved in the back end and to take action against them if we can.”

Cyxymu’s LiveJournal page wasn’t accessible, but a cached version showed that it was updated on Thursday with a message about the denial of service (DOS) attacks on his accounts on the US-based sites. “Now it’s obvious it’s a special attack against me and Georgians,” the message in Russian said.