POPULAR social networking sites Twitter and Facebook are under attack from cyber criminals allegedly targeting a single individual.

Online security firm Symantec today said it was monitoring a new wave of denial-of-service attacks against the sites, after a first round last night.

Twitter was taken offline by the attacks for several hours overnight. Facebook and LiveJournal also suffered problems.

CNET News reported the attacks may be targeting an individual with profiles on several social networking sites.

Facebook’s chief security officer Max Kelly told the site that the user, who uses the pseudonym “cyxymu”, was a pro-Georgian blogger.

“It was a simultaneous attack across a number of properties targeting him to keep his voice from being heard,” Mr Kelly said.

Georgia is a former member of the Soviet Union and last year was involved in an armed conflict with Russia.

The “cyxymu” profile is currently able to be viewed on Twitter and YouTube. It is down on Facebook and LiveJournal.

“Cyxymu” has previously written on LiveJournal of Russian visa restrictions on Georgian citizens and the ongoing conflict between Georgia and Abkhazia.

Last night a post on the official Twitter blog confirmed the attacks.

“We are defending against a denial-of-service attack, and will update status again shortly,” it said.

LiveJournal also confirmed an attack and said it suspected they were linked.

“The company cannot 100 per cent confirm that it is the same attack that plagued Twitter this morning, but it would be a huge coincidence if they aren’t tied to one another,” a spokesman said.

Sorry to quote the whole thing, but if true, this is fascinating! Conducting massive, multiple-network denial of service attacks to quiet one individual.